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 $60.61   3.385%   $62.6616   $62.66   $62.65   $62.70  
  Purchase #2 $36.33   4.549%   $37.9827   $37.98   $38.00   $38.00  
  Purchase #3 $164.86   5.233%   $173.4871   $173.49   $173.50   $173.50  
  Purchase #4 $221.91   7.518%   $238.5932   $238.59   $238.60   $238.60  
  Purchase #5 $79.74   10.665%   $88.2443   $88.24   $88.25   $88.20  
  Purchase #6 $189.37   3.239%   $195.5037   $195.50   $195.50   $195.50  
  Purchase #7 $79.32   13.726%   $90.2075   $90.21   $90.20   $90.20  
  7 purchase totals = $832.14       $886.6801   $886.67   $886.70   $886.70