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 $41.41   5.638%   $43.7447   $43.74   $43.75   $43.70  
  Purchase #2 $174.53   11.712%   $194.971   $194.97   $194.95   $195.00  
  Purchase #3 $114.39   4.444%   $119.4735   $119.47   $119.45   $119.50  
  Purchase #4 $101.38   7.276%   $108.7564   $108.76   $108.75   $108.80  
  Purchase #5 $108.34   7.791%   $116.7808   $116.78   $116.80   $116.80  
  Purchase #6 $227.55   8.239%   $246.2978   $246.30   $246.30   $246.30  
  Purchase #7 $76.99   9.823%   $84.5527   $84.55   $84.55   $84.60  
  7 purchase totals = $844.59       $914.5769   $914.57   $914.55   $914.70