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 $65.88   5.766%   $69.6786   $69.68   $69.70   $69.70  
  Purchase #2 $182.26   3.565%   $188.7576   $188.76   $188.75   $188.80  
  Purchase #3 $27.31   3.336%   $28.2211   $28.22   $28.20   $28.20  
  Purchase #4 $10.31   6.176%   $10.9467   $10.95   $10.95   $10.90  
  Purchase #5 $179.45   11.313%   $199.7512   $199.75   $199.75   $199.80  
  Purchase #6 $151.37   9.764%   $166.1498   $166.15   $166.15   $166.10  
  Purchase #7 $39.25   3.541%   $40.6398   $40.64   $40.65   $40.60  
  7 purchase totals = $655.83       $704.1448   $704.15   $704.15   $704.10