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 $206.84   11.503%   $230.6328   $230.63   $230.65   $230.60  
  Purchase #2 $61.29   3.211%   $63.258   $63.26   $63.25   $63.30  
  Purchase #3 $66.29   4.475%   $69.2565   $69.26   $69.25   $69.30  
  Purchase #4 $14.25   6.722%   $15.2079   $15.21   $15.20   $15.20  
  Purchase #5 $228.26   13.763%   $259.6754   $259.68   $259.70   $259.70  
  Purchase #6 $94.31   7.806%   $101.6718   $101.67   $101.65   $101.70  
  Purchase #7 $20.72   11.144%   $23.029   $23.03   $23.05   $23.00  
  7 purchase totals = $691.96       $762.7314   $762.74   $762.75   $762.80