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 $72.81   5.423%   $76.7585   $76.76   $76.75   $76.80  
  Purchase #2 $12.48   3.205%   $12.88   $12.88   $12.90   $12.90  
  Purchase #3 $197.89   5.203%   $208.1862   $208.19   $208.20   $208.20  
  Purchase #4 $53.50   13.192%   $60.5577   $60.56   $60.55   $60.60  
  Purchase #5 $216.71   5.686%   $229.0321   $229.03   $229.05   $229.00  
  Purchase #6 $20.47   8.827%   $22.2769   $22.28   $22.30   $22.30  
  Purchase #7 $101.49   8.394%   $110.0091   $110.01   $110.00   $110.00  
  7 purchase totals = $675.35       $719.7005   $719.71   $719.75   $719.80