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 $96.72   5.426%   $101.968   $101.97   $101.95   $102.00  
  Purchase #2 $232.95   6.382%   $247.8169   $247.82   $247.80   $247.80  
  Purchase #3 $59.65   12.619%   $67.1772   $67.18   $67.20   $67.20  
  Purchase #4 $238.55   5.811%   $252.4121   $252.41   $252.40   $252.40  
  Purchase #5 $138.95   10.737%   $153.8691   $153.87   $153.85   $153.90  
  Purchase #6 $205.34   5.849%   $217.3503   $217.35   $217.35   $217.40  
  Purchase #7 $173.32   11.383%   $193.049   $193.05   $193.05   $193.00  
  7 purchase totals = $1,145.48       $1,233.6426   $1,233.65   $1,233.60   $1,233.70