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 $73.36   3.606%   $76.0054   $76.01   $76.00   $76.00  
  Purchase #2 $219.41   11.804%   $245.3092   $245.31   $245.30   $245.30  
  Purchase #3 $112.29   3.406%   $116.1146   $116.11   $116.10   $116.10  
  Purchase #4 $104.31   5.406%   $109.949   $109.95   $109.95   $109.90  
  Purchase #5 $239.66   9.314%   $261.9819   $261.98   $262.00   $262.00  
  Purchase #6 $242.86   4.230%   $253.133   $253.13   $253.15   $253.10  
  Purchase #7 $188.77   9.234%   $206.201   $206.20   $206.20   $206.20  
  7 purchase totals = $1,180.66       $1,268.6941   $1,268.69   $1,268.70   $1,268.60