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 $59.95   3.524%   $62.0626   $62.06   $62.05   $62.10  
  Purchase #2 $207.74   10.371%   $229.2847   $229.28   $229.30   $229.30  
  Purchase #3 $190.54   3.399%   $197.0165   $197.02   $197.00   $197.00  
  Purchase #4 $156.37   9.107%   $170.6106   $170.61   $170.60   $170.60  
  Purchase #5 $79.60   11.653%   $88.8758   $88.88   $88.90   $88.90  
  Purchase #6 $24.47   4.741%   $25.6301   $25.63   $25.65   $25.60  
  Purchase #7 $10.91   5.669%   $11.5285   $11.53   $11.55   $11.50  
  7 purchase totals = $729.58       $785.0088   $785.01   $785.05   $785.00