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 $12.96   8.133%   $14.014   $14.01   $14.00   $14.00  
  Purchase #2 $53.91   12.469%   $60.632   $60.63   $60.65   $60.60  
  Purchase #3 $220.95   11.812%   $247.0486   $247.05   $247.05   $247.00  
  Purchase #4 $49.46   12.856%   $55.8186   $55.82   $55.80   $55.80  
  Purchase #5 $167.37   4.110%   $174.2489   $174.25   $174.25   $174.20  
  Purchase #6 $148.32   3.827%   $153.9962   $154.00   $154.00   $154.00  
  Purchase #7 $51.26   6.503%   $54.5934   $54.59   $54.60   $54.60  
  7 purchase totals = $704.23       $760.3517   $760.35   $760.35   $760.20