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 $44.97   3.143%   $46.3834   $46.38   $46.40   $46.40  
  Purchase #2 $134.33   13.269%   $152.1542   $152.15   $152.15   $152.20  
  Purchase #3 $59.75   3.851%   $62.051   $62.05   $62.05   $62.10  
  Purchase #4 $40.77   3.838%   $42.3348   $42.33   $42.35   $42.30  
  Purchase #5 $204.40   13.520%   $232.0349   $232.03   $232.05   $232.00  
  Purchase #6 $242.52   8.623%   $263.4325   $263.43   $263.45   $263.40  
  Purchase #7 $107.42   8.271%   $116.3047   $116.30   $116.30   $116.30  
  7 purchase totals = $834.16       $914.6955   $914.67   $914.75   $914.70