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 $224.48   9.482%   $245.7652   $245.77   $245.75   $245.80  
  Purchase #2 $176.78   10.562%   $195.4515   $195.45   $195.45   $195.50  
  Purchase #3 $157.75   8.563%   $171.2581   $171.26   $171.25   $171.30  
  Purchase #4 $114.38   3.127%   $117.9567   $117.96   $117.95   $118.00  
  Purchase #5 $25.67   7.564%   $27.6117   $27.61   $27.60   $27.60  
  Purchase #6 $197.29   4.299%   $205.7715   $205.77   $205.75   $205.80  
  Purchase #7 $116.69   12.125%   $130.8387   $130.84   $130.85   $130.80  
  7 purchase totals = $1,013.04       $1,094.6534   $1,094.66   $1,094.60   $1,094.80