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 $208.47   5.761%   $220.48   $220.48   $220.50   $220.50  
  Purchase #2 $232.43   5.585%   $245.4112   $245.41   $245.40   $245.40  
  Purchase #3 $156.97   10.584%   $173.5837   $173.58   $173.60   $173.60  
  Purchase #4 $22.55   11.385%   $25.1173   $25.12   $25.10   $25.10  
  Purchase #5 $116.67   11.181%   $129.7149   $129.71   $129.70   $129.70  
  Purchase #6 $163.94   13.222%   $185.6161   $185.62   $185.60   $185.60  
  Purchase #7 $122.42   11.115%   $136.027   $136.03   $136.05   $136.00  
  7 purchase totals = $1,023.45       $1,115.9502   $1,115.95   $1,115.95   $1,115.90