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 $64.25   7.342%   $68.9672   $68.97   $68.95   $69.00  
  Purchase #2 $208.83   8.111%   $225.7682   $225.77   $225.75   $225.80  
  Purchase #3 $67.97   4.289%   $70.8852   $70.89   $70.90   $70.90  
  Purchase #4 $166.63   10.192%   $183.6129   $183.61   $183.60   $183.60  
  Purchase #5 $104.28   11.227%   $115.9875   $115.99   $116.00   $116.00  
  Purchase #6 $108.83   6.255%   $115.6373   $115.64   $115.65   $115.60  
  Purchase #7 $133.36   8.765%   $145.049   $145.05   $145.05   $145.00  
  7 purchase totals = $854.15       $925.9073   $925.92   $925.90   $925.90