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 $247.65   7.793%   $266.9494   $266.95   $266.95   $266.90  
  Purchase #2 $125.62   3.644%   $130.1976   $130.20   $130.20   $130.20  
  Purchase #3 $112.40   5.750%   $118.863   $118.86   $118.85   $118.90  
  Purchase #4 $159.29   11.331%   $177.3391   $177.34   $177.35   $177.30  
  Purchase #5 $70.86   3.409%   $73.2756   $73.28   $73.30   $73.30  
  Purchase #6 $185.98   4.830%   $194.9628   $194.96   $194.95   $195.00  
  Purchase #7 $106.31   5.613%   $112.2772   $112.28   $112.30   $112.30  
  7 purchase totals = $1,008.11       $1,073.8647   $1,073.87   $1,073.90   $1,073.90