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 $46.86   4.214%   $48.8347   $48.83   $48.85   $48.80  
  Purchase #2 $58.25   8.705%   $63.3207   $63.32   $63.30   $63.30  
  Purchase #3 $27.61   11.369%   $30.749   $30.75   $30.75   $30.70  
  Purchase #4 $164.97   6.359%   $175.4604   $175.46   $175.45   $175.50  
  Purchase #5 $229.80   9.221%   $250.9899   $250.99   $251.00   $251.00  
  Purchase #6 $110.70   4.857%   $116.0767   $116.08   $116.10   $116.10  
  Purchase #7 $59.73   13.827%   $67.9889   $67.99   $68.00   $68.00  
  7 purchase totals = $697.92       $753.4203   $753.42   $753.45   $753.40