Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $169.55   3.649%   $175.7369   $175.74   $175.75   $175.70  
  Purchase #2 $232.47   11.856%   $260.0316   $260.03   $260.05   $260.00  
  Purchase #3 $248.92   3.259%   $257.0323   $257.03   $257.05   $257.00  
  Purchase #4 $146.80   7.647%   $158.0258   $158.03   $158.05   $158.00  
  Purchase #5 $227.48   11.121%   $252.7781   $252.78   $252.80   $252.80  
  Purchase #6 $99.94   4.151%   $104.0885   $104.09   $104.10   $104.10  
  Purchase #7 $217.95   3.261%   $225.0573   $225.06   $225.05   $225.10  
  7 purchase totals = $1,343.11       $1,432.7505   $1,432.76   $1,432.85   $1,432.70