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 $210.43   5.265%   $221.5091   $221.51   $221.50   $221.50  
  Purchase #2 $248.97   9.746%   $273.2346   $273.23   $273.25   $273.20  
  Purchase #3 $132.88   5.773%   $140.5512   $140.55   $140.55   $140.60  
  Purchase #4 $114.40   3.823%   $118.7735   $118.77   $118.75   $118.80  
  Purchase #5 $217.93   9.145%   $237.8597   $237.86   $237.85   $237.90  
  Purchase #6 $248.63   11.272%   $276.6556   $276.66   $276.65   $276.70  
  Purchase #7 $182.78   6.477%   $194.6187   $194.62   $194.60   $194.60  
  7 purchase totals = $1,356.02       $1,463.2024   $1,463.20   $1,463.15   $1,463.30