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 $107.51   10.644%   $118.9534   $118.95   $118.95   $119.00  
  Purchase #2 $44.27   13.382%   $50.1942   $50.19   $50.20   $50.20  
  Purchase #3 $14.56   7.314%   $15.6249   $15.62   $15.60   $15.60  
  Purchase #4 $129.86   6.770%   $138.6515   $138.65   $138.65   $138.70  
  Purchase #5 $59.60   10.264%   $65.7173   $65.72   $65.70   $65.70  
  Purchase #6 $198.33   8.716%   $215.6164   $215.62   $215.60   $215.60  
  Purchase #7 $120.91   5.362%   $127.3932   $127.39   $127.40   $127.40  
  7 purchase totals = $675.04       $732.1509   $732.14   $732.10   $732.20