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 $84.67   13.275%   $95.9099   $95.91   $95.90   $95.90  
  Purchase #2 $199.37   6.747%   $212.8215   $212.82   $212.80   $212.80  
  Purchase #3 $108.32   6.680%   $115.5558   $115.56   $115.55   $115.60  
  Purchase #4 $78.67   7.414%   $84.5026   $84.50   $84.50   $84.50  
  Purchase #5 $245.42   11.120%   $272.7107   $272.71   $272.70   $272.70  
  Purchase #6 $227.41   5.757%   $240.502   $240.50   $240.50   $240.50  
  Purchase #7 $202.28   5.475%   $213.3548   $213.35   $213.35   $213.40  
  7 purchase totals = $1,146.14       $1,235.3573   $1,235.35   $1,235.30   $1,235.40