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 $62.84   8.159%   $67.9671   $67.97   $67.95   $68.00  
  Purchase #2 $234.25   13.561%   $266.0166   $266.02   $266.00   $266.00  
  Purchase #3 $125.43   5.427%   $132.2371   $132.24   $132.25   $132.20  
  Purchase #4 $152.71   6.304%   $162.3368   $162.34   $162.35   $162.30  
  Purchase #5 $75.79   6.481%   $80.7019   $80.70   $80.70   $80.70  
  Purchase #6 $149.29   8.202%   $161.5348   $161.53   $161.55   $161.50  
  Purchase #7 $83.66   9.353%   $91.4847   $91.48   $91.50   $91.50  
  7 purchase totals = $883.97       $962.2790   $962.28   $962.30   $962.20