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 $87.88   9.542%   $96.2655   $96.27   $96.25   $96.30  
  Purchase #2 $26.63   5.563%   $28.1114   $28.11   $28.10   $28.10  
  Purchase #3 $167.95   7.687%   $180.8603   $180.86   $180.85   $180.90  
  Purchase #4 $240.92   3.285%   $248.8342   $248.83   $248.85   $248.80  
  Purchase #5 $58.88   11.211%   $65.481   $65.48   $65.50   $65.50  
  Purchase #6 $68.40   12.327%   $76.8317   $76.83   $76.85   $76.80  
  Purchase #7 $154.60   13.830%   $175.9812   $175.98   $176.00   $176.00  
  7 purchase totals = $805.26       $872.3653   $872.36   $872.40   $872.40