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 $71.93   5.654%   $75.9969   $76.00   $76.00   $76.00  
  Purchase #2 $193.27   7.261%   $207.3033   $207.30   $207.30   $207.30  
  Purchase #3 $202.98   6.129%   $215.4206   $215.42   $215.40   $215.40  
  Purchase #4 $34.78   13.350%   $39.4231   $39.42   $39.40   $39.40  
  Purchase #5 $151.77   10.575%   $167.8197   $167.82   $167.80   $167.80  
  Purchase #6 $36.65   11.833%   $40.9868   $40.99   $41.00   $41.00  
  Purchase #7 $140.32   12.703%   $158.1448   $158.14   $158.15   $158.10  
  7 purchase totals = $831.70       $905.0952   $905.09   $905.05   $905.00