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 $72.40   4.703%   $75.805   $75.81   $75.80   $75.80  
  Purchase #2 $149.79   11.243%   $166.6309   $166.63   $166.65   $166.60  
  Purchase #3 $96.65   5.565%   $102.0286   $102.03   $102.05   $102.00  
  Purchase #4 $115.48   5.375%   $121.6871   $121.69   $121.70   $121.70  
  Purchase #5 $55.63   4.195%   $57.9637   $57.96   $57.95   $58.00  
  Purchase #6 $144.47   11.702%   $161.3759   $161.38   $161.40   $161.40  
  Purchase #7 $132.97   5.440%   $140.2036   $140.20   $140.20   $140.20  
  7 purchase totals = $767.39       $825.6948   $825.70   $825.75   $825.70