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 $69.94   8.225%   $75.6926   $75.69   $75.70   $75.70  
  Purchase #2 $59.56   9.611%   $65.2843   $65.28   $65.30   $65.30  
  Purchase #3 $208.63   5.203%   $219.485   $219.49   $219.50   $219.50  
  Purchase #4 $178.44   5.390%   $188.0579   $188.06   $188.05   $188.10  
  Purchase #5 $148.82   11.774%   $166.3421   $166.34   $166.35   $166.30  
  Purchase #6 $247.59   10.694%   $274.0673   $274.07   $274.05   $274.10  
  Purchase #7 $15.84   13.502%   $17.9787   $17.98   $18.00   $18.00  
  7 purchase totals = $928.82       $1,006.9079   $1,006.91   $1,006.95   $1,007.00