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 $117.82   6.733%   $125.7528   $125.75   $125.75   $125.80  
  Purchase #2 $14.80   4.208%   $15.4228   $15.42   $15.40   $15.40  
  Purchase #3 $57.31   11.817%   $64.0823   $64.08   $64.10   $64.10  
  Purchase #4 $192.75   7.856%   $207.8924   $207.89   $207.90   $207.90  
  Purchase #5 $250.34   5.351%   $263.7357   $263.74   $263.75   $263.70  
  Purchase #6 $151.90   12.356%   $170.6688   $170.67   $170.65   $170.70  
  Purchase #7 $84.49   13.321%   $95.7449   $95.74   $95.75   $95.70  
  7 purchase totals = $869.41       $943.2997   $943.29   $943.30   $943.30