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 $70.49   8.160%   $76.242   $76.24   $76.25   $76.20  
  Purchase #2 $56.62   7.796%   $61.0341   $61.03   $61.05   $61.00  
  Purchase #3 $93.32   8.353%   $101.115   $101.12   $101.10   $101.10  
  Purchase #4 $185.63   5.402%   $195.6577   $195.66   $195.65   $195.70  
  Purchase #5 $115.54   8.211%   $125.027   $125.03   $125.05   $125.00  
  Purchase #6 $222.91   8.688%   $242.2764   $242.28   $242.30   $242.30  
  Purchase #7 $129.31   13.698%   $147.0229   $147.02   $147.00   $147.00  
  7 purchase totals = $873.82       $948.3751   $948.38   $948.40   $948.30