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 $92.32   3.582%   $95.6269   $95.63   $95.65   $95.60  
  Purchase #2 $179.76   12.569%   $202.354   $202.35   $202.35   $202.40  
  Purchase #3 $37.89   11.165%   $42.1204   $42.12   $42.10   $42.10  
  Purchase #4 $58.60   6.622%   $62.4805   $62.48   $62.50   $62.50  
  Purchase #5 $201.91   7.618%   $217.2915   $217.29   $217.30   $217.30  
  Purchase #6 $159.40   6.742%   $170.1467   $170.15   $170.15   $170.10  
  Purchase #7 $61.92   4.319%   $64.5943   $64.59   $64.60   $64.60  
  7 purchase totals = $791.80       $854.6143   $854.61   $854.65   $854.60