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 $58.38   4.403%   $60.9505   $60.95   $60.95   $61.00  
  Purchase #2 $125.64   9.862%   $138.0306   $138.03   $138.05   $138.00  
  Purchase #3 $6.54   7.532%   $7.0326   $7.03   $7.05   $7.00  
  Purchase #4 $176.67   8.385%   $191.4838   $191.48   $191.50   $191.50  
  Purchase #5 $29.42   13.165%   $33.2931   $33.29   $33.30   $33.30  
  Purchase #6 $206.82   11.804%   $231.233   $231.23   $231.25   $231.20  
  Purchase #7 $94.44   8.539%   $102.5042   $102.50   $102.50   $102.50  
  7 purchase totals = $697.91       $764.5278   $764.51   $764.60   $764.50