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 $69.67   9.335%   $76.1737   $76.17   $76.15   $76.20  
  Purchase #2 $189.92   12.575%   $213.8024   $213.80   $213.80   $213.80  
  Purchase #3 $233.51   12.778%   $263.3479   $263.35   $263.35   $263.30  
  Purchase #4 $217.60   5.748%   $230.1076   $230.11   $230.10   $230.10  
  Purchase #5 $240.77   5.397%   $253.7644   $253.76   $253.75   $253.80  
  Purchase #6 $53.59   9.401%   $58.628   $58.63   $58.65   $58.60  
  Purchase #7 $208.45   9.349%   $227.938   $227.94   $227.95   $227.90  
  7 purchase totals = $1,213.51       $1,323.7620   $1,323.76   $1,323.75   $1,323.70