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 $208.54   13.153%   $235.9693   $235.97   $235.95   $236.00  
  Purchase #2 $215.62   9.592%   $236.3023   $236.30   $236.30   $236.30  
  Purchase #3 $43.37   6.584%   $46.2255   $46.23   $46.25   $46.20  
  Purchase #4 $25.94   8.735%   $28.2059   $28.21   $28.20   $28.20  
  Purchase #5 $158.82   9.167%   $173.379   $173.38   $173.40   $173.40  
  Purchase #6 $100.53   12.822%   $113.42   $113.42   $113.40   $113.40  
  Purchase #7 $245.33   6.251%   $260.6656   $260.67   $260.65   $260.70  
  7 purchase totals = $998.15       $1,094.1676   $1,094.18   $1,094.15   $1,094.20