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 $192.64   4.362%   $201.043   $201.04   $201.05   $201.00  
  Purchase #2 $112.40   3.578%   $116.4217   $116.42   $116.40   $116.40  
  Purchase #3 $95.27   7.715%   $102.6201   $102.62   $102.60   $102.60  
  Purchase #4 $190.27   11.450%   $212.0559   $212.06   $212.05   $212.10  
  Purchase #5 $221.38   9.597%   $242.6258   $242.63   $242.65   $242.60  
  Purchase #6 $165.93   10.843%   $183.9218   $183.92   $183.90   $183.90  
  Purchase #7 $202.80   6.219%   $215.4121   $215.41   $215.40   $215.40  
  7 purchase totals = $1,180.69       $1,274.1004   $1,274.10   $1,274.05   $1,274.00