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 $207.32   12.638%   $233.5211   $233.52   $233.50   $233.50  
  Purchase #2 $94.76   4.108%   $98.6527   $98.65   $98.65   $98.70  
  Purchase #3 $45.37   9.856%   $49.8417   $49.84   $49.85   $49.80  
  Purchase #4 $184.38   5.327%   $194.2019   $194.20   $194.20   $194.20  
  Purchase #5 $60.43   3.701%   $62.6665   $62.67   $62.65   $62.70  
  Purchase #6 $111.32   4.726%   $116.581   $116.58   $116.60   $116.60  
  Purchase #7 $103.66   10.208%   $114.2416   $114.24   $114.25   $114.20  
  7 purchase totals = $807.24       $869.7065   $869.70   $869.70   $869.70