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 $59.41   5.735%   $62.8172   $62.82   $62.80   $62.80  
  Purchase #2 $187.37   4.182%   $195.2058   $195.21   $195.20   $195.20  
  Purchase #3 $92.67   5.733%   $97.9828   $97.98   $98.00   $98.00  
  Purchase #4 $132.84   10.167%   $146.3458   $146.35   $146.35   $146.30  
  Purchase #5 $139.25   10.835%   $154.3377   $154.34   $154.35   $154.30  
  Purchase #6 $8.48   9.694%   $9.3021   $9.30   $9.30   $9.30  
  Purchase #7 $141.87   8.565%   $154.0212   $154.02   $154.00   $154.00  
  7 purchase totals = $761.89       $820.0126   $820.02   $820.00   $819.90