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 $184.55   5.482%   $194.667   $194.67   $194.65   $194.70  
  Purchase #2 $50.69   6.865%   $54.1699   $54.17   $54.15   $54.20  
  Purchase #3 $234.92   3.286%   $242.6395   $242.64   $242.65   $242.60  
  Purchase #4 $213.43   12.563%   $240.2432   $240.24   $240.25   $240.20  
  Purchase #5 $162.76   3.141%   $167.8723   $167.87   $167.85   $167.90  
  Purchase #6 $226.73   4.325%   $236.5361   $236.54   $236.55   $236.50  
  Purchase #7 $208.64   4.650%   $218.3418   $218.34   $218.35   $218.30  
  7 purchase totals = $1,281.72       $1,354.4698   $1,354.47   $1,354.45   $1,354.40