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 $59.50   6.252%   $63.2199   $63.22   $63.20   $63.20  
  Purchase #2 $104.59   5.593%   $110.4397   $110.44   $110.45   $110.40  
  Purchase #3 $24.31   7.316%   $26.0885   $26.09   $26.10   $26.10  
  Purchase #4 $59.95   4.431%   $62.6064   $62.61   $62.60   $62.60  
  Purchase #5 $97.69   11.501%   $108.9253   $108.93   $108.95   $108.90  
  Purchase #6 $114.72   8.368%   $124.3198   $124.32   $124.30   $124.30  
  Purchase #7 $61.54   10.250%   $67.8479   $67.85   $67.85   $67.80  
  7 purchase totals = $522.30       $563.4475   $563.46   $563.45   $563.30