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	$206.26	7.249%	$221.2118	$221.21	$221.20	$221.20
Purchase #2	$72.91	11.531%	$81.3173	$81.32	$81.30	$81.30
Purchase #3	$243.47	7.856%	$262.597	$262.60	$262.60	$262.60
Purchase #4	$173.91	9.357%	$190.1828	$190.18	$190.20	$190.20
Purchase #5	$82.91	9.105%	$90.459	$90.46	$90.45	$90.50
Purchase #6	$112.66	13.483%	$127.8499	$127.85	$127.85	$127.80
Purchase #7	$115.29	12.402%	$129.5883	$129.59	$129.60	$129.60
7 purchase totals =	$1,007.41		$1,103.2061	$1,103.21	$1,103.20	$1,103.20