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 $167.69   9.697%   $183.9509   $183.95   $183.95   $184.00  
  Purchase #2 $126.95   4.239%   $132.3314   $132.33   $132.35   $132.30  
  Purchase #3 $140.93   8.814%   $153.3516   $153.35   $153.35   $153.40  
  Purchase #4 $71.79   6.193%   $76.236   $76.24   $76.25   $76.20  
  Purchase #5 $245.73   5.254%   $258.6407   $258.64   $258.65   $258.60  
  Purchase #6 $181.87   7.480%   $195.4739   $195.47   $195.45   $195.50  
  Purchase #7 $174.82   6.129%   $185.5347   $185.53   $185.55   $185.50  
  7 purchase totals = $1,109.78       $1,185.5192   $1,185.51   $1,185.55   $1,185.50