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 $88.47   9.525%   $96.8968   $96.90   $96.90   $96.90  
  Purchase #2 $191.89   4.826%   $201.1506   $201.15   $201.15   $201.20  
  Purchase #3 $116.93   10.865%   $129.6344   $129.63   $129.65   $129.60  
  Purchase #4 $178.95   8.824%   $194.7405   $194.74   $194.75   $194.70  
  Purchase #5 $54.93   4.671%   $57.4958   $57.50   $57.50   $57.50  
  Purchase #6 $113.79   4.821%   $119.2758   $119.28   $119.30   $119.30  
  Purchase #7 $188.78   10.156%   $207.9525   $207.95   $207.95   $208.00  
  7 purchase totals = $933.74       $1,007.1464   $1,007.15   $1,007.20   $1,007.20