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 $176.86   11.874%   $197.8604   $197.86   $197.85   $197.90  
  Purchase #2 $112.90   13.667%   $128.33   $128.33   $128.35   $128.30  
  Purchase #3 $102.53   13.344%   $116.2116   $116.21   $116.20   $116.20  
  Purchase #4 $212.60   4.210%   $221.5505   $221.55   $221.55   $221.60  
  Purchase #5 $96.88   5.172%   $101.8906   $101.89   $101.90   $101.90  
  Purchase #6 $165.50   11.583%   $184.6699   $184.67   $184.65   $184.70  
  Purchase #7 $182.71   6.797%   $195.1288   $195.13   $195.15   $195.10  
  7 purchase totals = $1,049.98       $1,145.6418   $1,145.64   $1,145.65   $1,145.70