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 $65.60   8.273%   $71.0271   $71.03   $71.05   $71.00  
  Purchase #2 $117.61   7.119%   $125.9827   $125.98   $126.00   $126.00  
  Purchase #3 $60.33   3.523%   $62.4554   $62.46   $62.45   $62.50  
  Purchase #4 $12.33   10.575%   $13.6339   $13.63   $13.65   $13.60  
  Purchase #5 $117.80   13.541%   $133.7513   $133.75   $133.75   $133.80  
  Purchase #6 $233.34   7.502%   $250.8452   $250.85   $250.85   $250.80  
  Purchase #7 $92.34   7.158%   $98.9497   $98.95   $98.95   $98.90  
  7 purchase totals = $699.35       $756.6453   $756.65   $756.70   $756.60