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 $112.57   5.300%   $118.5362   $118.54   $118.55   $118.50  
  Purchase #2 $247.53   5.523%   $261.2011   $261.20   $261.20   $261.20  
  Purchase #3 $95.26   12.135%   $106.8198   $106.82   $106.80   $106.80  
  Purchase #4 $119.58   11.657%   $133.5194   $133.52   $133.50   $133.50  
  Purchase #5 $117.79   12.519%   $132.5361   $132.54   $132.55   $132.50  
  Purchase #6 $194.80   13.543%   $221.1818   $221.18   $221.20   $221.20  
  Purchase #7 $47.54   4.180%   $49.5272   $49.53   $49.55   $49.50  
  7 purchase totals = $935.07       $1,023.3216   $1,023.33   $1,023.35   $1,023.20