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 $63.99   13.444%   $72.5928   $72.59   $72.60   $72.60  
  Purchase #2 $244.40   7.284%   $262.2021   $262.20   $262.20   $262.20  
  Purchase #3 $7.62   12.599%   $8.58   $8.58   $8.60   $8.60  
  Purchase #4 $117.76   8.239%   $127.4622   $127.46   $127.45   $127.50  
  Purchase #5 $173.96   13.684%   $197.7647   $197.76   $197.75   $197.80  
  Purchase #6 $93.48   11.613%   $104.3358   $104.34   $104.35   $104.30  
  Purchase #7 $167.48   8.817%   $182.2467   $182.25   $182.25   $182.20  
  7 purchase totals = $868.69       $955.1843   $955.18   $955.20   $955.20