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 $82.80   13.694%   $94.1386   $94.14   $94.15   $94.10  
  Purchase #2 $117.72   6.709%   $125.6178   $125.62   $125.60   $125.60  
  Purchase #3 $42.78   10.264%   $47.1709   $47.17   $47.15   $47.20  
  Purchase #4 $210.55   7.346%   $226.017   $226.02   $226.00   $226.00  
  Purchase #5 $107.49   4.793%   $112.642   $112.64   $112.65   $112.60  
  Purchase #6 $116.51   4.709%   $121.9965   $122.00   $122.00   $122.00  
  Purchase #7 $235.96   9.449%   $258.2559   $258.26   $258.25   $258.30  
  7 purchase totals = $913.81       $985.8387   $985.85   $985.80   $985.80