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 $86.71   5.687%   $91.6412   $91.64   $91.65   $91.60  
  Purchase #2 $66.94   13.532%   $75.9983   $76.00   $76.00   $76.00  
  Purchase #3 $59.49   4.774%   $62.3301   $62.33   $62.35   $62.30  
  Purchase #4 $159.92   7.706%   $172.2434   $172.24   $172.25   $172.20  
  Purchase #5 $68.69   4.713%   $71.9274   $71.93   $71.95   $71.90  
  Purchase #6 $212.60   5.422%   $224.1272   $224.13   $224.15   $224.10  
  Purchase #7 $105.26   10.653%   $116.4733   $116.47   $116.45   $116.50  
  7 purchase totals = $759.61       $814.7409   $814.74   $814.80   $814.60