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 $45.73   3.527%   $47.3429   $47.34   $47.35   $47.30  
  Purchase #2 $204.57   6.419%   $217.7013   $217.70   $217.70   $217.70  
  Purchase #3 $204.82   10.162%   $225.6338   $225.63   $225.65   $225.60  
  Purchase #4 $120.49   5.505%   $127.123   $127.12   $127.10   $127.10  
  Purchase #5 $232.41   3.481%   $240.5002   $240.50   $240.50   $240.50  
  Purchase #6 $164.85   3.687%   $170.928   $170.93   $170.95   $170.90  
  Purchase #7 $160.85   10.199%   $177.2551   $177.26   $177.25   $177.30  
  7 purchase totals = $1,133.72       $1,206.4843   $1,206.48   $1,206.50   $1,206.40