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 $56.62   10.717%   $62.688   $62.69   $62.70   $62.70  
  Purchase #2 $240.37   9.574%   $263.383   $263.38   $263.40   $263.40  
  Purchase #3 $245.90   7.414%   $264.131   $264.13   $264.15   $264.10  
  Purchase #4 $201.48   11.527%   $224.7046   $224.70   $224.70   $224.70  
  Purchase #5 $230.60   5.339%   $242.9117   $242.91   $242.90   $242.90  
  Purchase #6 $229.97   5.434%   $242.4666   $242.47   $242.45   $242.50  
  Purchase #7 $214.85   7.193%   $230.3042   $230.30   $230.30   $230.30  
  7 purchase totals = $1,419.79       $1,530.5891   $1,530.58   $1,530.60   $1,530.60