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 $114.83   7.326%   $123.2424   $123.24   $123.25   $123.20  
  Purchase #2 $231.91   9.268%   $253.4034   $253.40   $253.40   $253.40  
  Purchase #3 $68.40   10.561%   $75.6237   $75.62   $75.60   $75.60  
  Purchase #4 $17.63   3.290%   $18.21   $18.21   $18.20   $18.20  
  Purchase #5 $221.27   9.120%   $241.4498   $241.45   $241.45   $241.40  
  Purchase #6 $117.91   5.486%   $124.3785   $124.38   $124.40   $124.40  
  Purchase #7 $204.37   13.783%   $232.5383   $232.54   $232.55   $232.50  
  7 purchase totals = $976.32       $1,068.8461   $1,068.84   $1,068.85   $1,068.70