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 $67.49   5.196%   $70.9968   $71.00   $71.00   $71.00  
  Purchase #2 $210.32   10.474%   $232.3489   $232.35   $232.35   $232.30  
  Purchase #3 $10.26   5.105%   $10.7838   $10.78   $10.80   $10.80  
  Purchase #4 $187.27   11.540%   $208.881   $208.88   $208.90   $208.90  
  Purchase #5 $95.31   3.216%   $98.3752   $98.38   $98.40   $98.40  
  Purchase #6 $143.41   9.329%   $156.7887   $156.79   $156.80   $156.80  
  Purchase #7 $164.36   11.433%   $183.1513   $183.15   $183.15   $183.20  
  7 purchase totals = $878.42       $961.3257   $961.33   $961.40   $961.40