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 $119.28   4.155%   $124.2361   $124.24   $124.25   $124.20  
  Purchase #2 $183.50   6.596%   $195.6037   $195.60   $195.60   $195.60  
  Purchase #3 $42.86   10.420%   $47.326   $47.33   $47.35   $47.30  
  Purchase #4 $188.79   7.705%   $203.3363   $203.34   $203.35   $203.30  
  Purchase #5 $45.49   3.436%   $47.053   $47.05   $47.05   $47.10  
  Purchase #6 $59.66   9.303%   $65.2102   $65.21   $65.20   $65.20  
  Purchase #7 $58.73   4.439%   $61.337   $61.34   $61.35   $61.30  
  7 purchase totals = $698.31       $744.1023   $744.11   $744.15   $744.00