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 $64.88   5.752%   $68.6119   $68.61   $68.60   $68.60  
  Purchase #2 $66.39   8.479%   $72.0192   $72.02   $72.00   $72.00  
  Purchase #3 $82.90   13.847%   $94.3792   $94.38   $94.40   $94.40  
  Purchase #4 $127.75   6.650%   $136.2454   $136.25   $136.25   $136.20  
  Purchase #5 $150.35   7.746%   $161.9961   $162.00   $162.00   $162.00  
  Purchase #6 $111.35   7.439%   $119.6333   $119.63   $119.65   $119.60  
  Purchase #7 $203.60   5.749%   $215.305   $215.31   $215.30   $215.30  
  7 purchase totals = $807.22       $868.1901   $868.20   $868.20   $868.10