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 $44.43   8.312%   $48.123   $48.12   $48.10   $48.10  
  Purchase #2 $158.73   6.153%   $168.4967   $168.50   $168.50   $168.50  
  Purchase #3 $66.60   12.674%   $75.0409   $75.04   $75.05   $75.00  
  Purchase #4 $212.91   4.695%   $222.9061   $222.91   $222.90   $222.90  
  Purchase #5 $26.46   10.137%   $29.1423   $29.14   $29.15   $29.10  
  Purchase #6 $213.97   4.541%   $223.6864   $223.69   $223.70   $223.70  
  Purchase #7 $163.84   9.172%   $178.8674   $178.87   $178.85   $178.90  
  7 purchase totals = $886.94       $946.2628   $946.27   $946.25   $946.20