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 $46.84   4.505%   $48.9501   $48.95   $48.95   $49.00  
  Purchase #2 $142.61   13.566%   $161.9565   $161.96   $161.95   $162.00  
  Purchase #3 $164.34   13.862%   $187.1208   $187.12   $187.10   $187.10  
  Purchase #4 $202.32   4.179%   $210.775   $210.78   $210.80   $210.80  
  Purchase #5 $154.53   6.384%   $164.3952   $164.40   $164.40   $164.40  
  Purchase #6 $69.51   6.535%   $74.0525   $74.05   $74.05   $74.10  
  Purchase #7 $235.68   5.800%   $249.3494   $249.35   $249.35   $249.30  
  7 purchase totals = $1,015.83       $1,096.5995   $1,096.61   $1,096.60   $1,096.70