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 $69.73   4.590%   $72.9306   $72.93   $72.95   $72.90  
  Purchase #2 $133.39   13.873%   $151.8952   $151.90   $151.90   $151.90  
  Purchase #3 $247.42   13.451%   $280.7005   $280.70   $280.70   $280.70  
  Purchase #4 $103.45   10.772%   $114.5936   $114.59   $114.60   $114.60  
  Purchase #5 $204.97   9.448%   $224.3356   $224.34   $224.35   $224.30  
  Purchase #6 $106.36   8.732%   $115.6474   $115.65   $115.65   $115.60  
  Purchase #7 $69.36   8.272%   $75.0975   $75.10   $75.10   $75.10  
  7 purchase totals = $934.68       $1,035.2004   $1,035.21   $1,035.25   $1,035.10