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 $208.26   4.157%   $216.9174   $216.92   $216.90   $216.90  
  Purchase #2 $113.27   5.576%   $119.5859   $119.59   $119.60   $119.60  
  Purchase #3 $202.51   5.288%   $213.2187   $213.22   $213.20   $213.20  
  Purchase #4 $218.58   9.253%   $238.8052   $238.81   $238.80   $238.80  
  Purchase #5 $240.67   7.805%   $259.4543   $259.45   $259.45   $259.50  
  Purchase #6 $236.45   4.187%   $246.3502   $246.35   $246.35   $246.40  
  Purchase #7 $48.30   6.733%   $51.552   $51.55   $51.55   $51.60  
  7 purchase totals = $1,268.04       $1,345.8837   $1,345.89   $1,345.85   $1,346.00