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 $233.62   12.381%   $262.5445   $262.54   $262.55   $262.50  
  Purchase #2 $154.61   4.716%   $161.9014   $161.90   $161.90   $161.90  
  Purchase #3 $60.90   9.302%   $66.5649   $66.56   $66.55   $66.60  
  Purchase #4 $244.38   5.191%   $257.0658   $257.07   $257.05   $257.10  
  Purchase #5 $150.30   4.296%   $156.7569   $156.76   $156.75   $156.80  
  Purchase #6 $178.87   7.770%   $192.7682   $192.77   $192.75   $192.80  
  Purchase #7 $84.42   10.117%   $92.9608   $92.96   $92.95   $93.00  
  7 purchase totals = $1,107.10       $1,190.5625   $1,190.56   $1,190.50   $1,190.70