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 $84.89   11.674%   $94.8001   $94.80   $94.80   $94.80  
  Purchase #2 $217.29   4.323%   $226.6834   $226.68   $226.70   $226.70  
  Purchase #3 $184.38   13.327%   $208.9523   $208.95   $208.95   $209.00  
  Purchase #4 $197.99   4.175%   $206.2561   $206.26   $206.25   $206.30  
  Purchase #5 $12.62   5.141%   $13.2688   $13.27   $13.25   $13.30  
  Purchase #6 $219.54   11.226%   $244.1856   $244.19   $244.20   $244.20  
  Purchase #7 $182.81   4.783%   $191.5538   $191.55   $191.55   $191.60  
  7 purchase totals = $1,099.52       $1,185.7001   $1,185.70   $1,185.70   $1,185.90