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 $62.95   8.281%   $68.1629   $68.16   $68.15   $68.20  
  Purchase #2 $185.82   10.219%   $204.8089   $204.81   $204.80   $204.80  
  Purchase #3 $71.26   9.565%   $78.076   $78.08   $78.10   $78.10  
  Purchase #4 $51.70   11.713%   $57.7556   $57.76   $57.75   $57.80  
  Purchase #5 $94.38   7.532%   $101.4887   $101.49   $101.50   $101.50  
  Purchase #6 $89.86   3.645%   $93.1354   $93.14   $93.15   $93.10  
  Purchase #7 $134.47   4.802%   $140.9272   $140.93   $140.95   $140.90  
  7 purchase totals = $690.44       $744.3547   $744.37   $744.40   $744.40