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 $202.38   4.234%   $210.9488   $210.95   $210.95   $210.90  
  Purchase #2 $86.77   10.869%   $96.201   $96.20   $96.20   $96.20  
  Purchase #3 $80.89   7.235%   $86.7424   $86.74   $86.75   $86.70  
  Purchase #4 $73.62   12.626%   $82.9153   $82.92   $82.90   $82.90  
  Purchase #5 $72.32   5.838%   $76.542   $76.54   $76.55   $76.50  
  Purchase #6 $222.53   12.164%   $249.5985   $249.60   $249.60   $249.60  
  Purchase #7 $210.83   9.181%   $230.1863   $230.19   $230.20   $230.20  
  7 purchase totals = $949.34       $1,033.1343   $1,033.14   $1,033.15   $1,033.00