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 $194.68   5.385%   $205.1635   $205.16   $205.15   $205.20  
  Purchase #2 $232.61   13.578%   $264.1938   $264.19   $264.20   $264.20  
  Purchase #3 $153.86   6.266%   $163.5009   $163.50   $163.50   $163.50  
  Purchase #4 $244.96   3.524%   $253.5924   $253.59   $253.60   $253.60  
  Purchase #5 $102.75   11.210%   $114.2683   $114.27   $114.25   $114.30  
  Purchase #6 $226.79   8.271%   $245.5478   $245.55   $245.55   $245.50  
  Purchase #7 $121.48   4.654%   $127.1337   $127.13   $127.15   $127.10  
  7 purchase totals = $1,277.13       $1,373.4004   $1,373.39   $1,373.40   $1,373.40