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 $112.38   5.246%   $118.2755   $118.28   $118.30   $118.30  
  Purchase #2 $173.51   13.754%   $197.3746   $197.37   $197.35   $197.40  
  Purchase #3 $29.88   7.769%   $32.2014   $32.20   $32.20   $32.20  
  Purchase #4 $239.39   7.674%   $257.7608   $257.76   $257.75   $257.80  
  Purchase #5 $182.64   5.734%   $193.1126   $193.11   $193.10   $193.10  
  Purchase #6 $103.47   4.721%   $108.3548   $108.35   $108.35   $108.40  
  Purchase #7 $195.82   11.245%   $217.84   $217.84   $217.85   $217.80  
  7 purchase totals = $1,037.09       $1,124.9197   $1,124.91   $1,124.90   $1,125.00