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 $185.50   11.216%   $206.3057   $206.31   $206.30   $206.30  
  Purchase #2 $85.29   11.210%   $94.851   $94.85   $94.85   $94.90  
  Purchase #3 $85.62   10.409%   $94.5322   $94.53   $94.55   $94.50  
  Purchase #4 $21.98   7.800%   $23.6944   $23.69   $23.70   $23.70  
  Purchase #5 $18.90   3.570%   $19.5747   $19.57   $19.55   $19.60  
  Purchase #6 $68.75   11.433%   $76.6102   $76.61   $76.60   $76.60  
  Purchase #7 $228.67   12.111%   $256.3642   $256.36   $256.35   $256.40  
  7 purchase totals = $694.71       $771.9324   $771.92   $771.90   $772.00