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 $67.55   11.364%   $75.2264   $75.23   $75.25   $75.20  
  Purchase #2 $190.79   7.541%   $205.1775   $205.18   $205.20   $205.20  
  Purchase #3 $32.56   11.175%   $36.1986   $36.20   $36.20   $36.20  
  Purchase #4 $150.26   5.510%   $158.5393   $158.54   $158.55   $158.50  
  Purchase #5 $177.98   10.317%   $196.3422   $196.34   $196.35   $196.30  
  Purchase #6 $148.27   8.773%   $161.2777   $161.28   $161.30   $161.30  
  Purchase #7 $243.83   11.549%   $271.9899   $271.99   $272.00   $272.00  
  7 purchase totals = $1,011.24       $1,104.7516   $1,104.76   $1,104.85   $1,104.70