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 $86.98   11.703%   $97.1593   $97.16   $97.15   $97.20  
  Purchase #2 $148.62   10.116%   $163.6544   $163.65   $163.65   $163.70  
  Purchase #3 $45.37   4.350%   $47.3436   $47.34   $47.35   $47.30  
  Purchase #4 $249.34   8.252%   $269.9155   $269.92   $269.90   $269.90  
  Purchase #5 $242.26   8.274%   $262.3046   $262.30   $262.30   $262.30  
  Purchase #6 $159.98   7.413%   $171.8393   $171.84   $171.85   $171.80  
  Purchase #7 $221.48   8.497%   $240.2992   $240.30   $240.30   $240.30  
  7 purchase totals = $1,154.03       $1,252.5159   $1,252.51   $1,252.50   $1,252.50