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 $184.59   6.126%   $195.898   $195.90   $195.90   $195.90  
  Purchase #2 $242.70   11.499%   $270.6081   $270.61   $270.60   $270.60  
  Purchase #3 $72.81   11.513%   $81.1926   $81.19   $81.20   $81.20  
  Purchase #4 $185.96   12.349%   $208.9242   $208.92   $208.90   $208.90  
  Purchase #5 $216.95   3.682%   $224.9381   $224.94   $224.95   $224.90  
  Purchase #6 $85.98   7.584%   $92.5007   $92.50   $92.50   $92.50  
  Purchase #7 $180.84   7.407%   $194.2348   $194.23   $194.25   $194.20  
  7 purchase totals = $1,169.83       $1,268.2965   $1,268.29   $1,268.30   $1,268.20