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 $85.64   11.795%   $95.7412   $95.74   $95.75   $95.70  
  Purchase #2 $214.41   10.850%   $237.6735   $237.67   $237.65   $237.70  
  Purchase #3 $170.87   7.611%   $183.8749   $183.87   $183.85   $183.90  
  Purchase #4 $59.98   10.472%   $66.2611   $66.26   $66.25   $66.30  
  Purchase #5 $29.94   12.859%   $33.79   $33.79   $33.80   $33.80  
  Purchase #6 $95.35   3.655%   $98.835   $98.84   $98.85   $98.80  
  Purchase #7 $19.89   8.139%   $21.5088   $21.51   $21.50   $21.50  
  7 purchase totals = $676.08       $737.6845   $737.68   $737.65   $737.70