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	$184.31	13.670%	$209.5052	$209.51	$209.50	$209.50
Purchase #2	$119.77	6.686%	$127.7778	$127.78	$127.80	$127.80
Purchase #3	$143.31	6.766%	$153.0064	$153.01	$153.00	$153.00
Purchase #4	$117.78	4.154%	$122.6726	$122.67	$122.65	$122.70
Purchase #5	$83.26	12.312%	$93.511	$93.51	$93.50	$93.50
Purchase #6	$211.77	10.632%	$234.2854	$234.29	$234.30	$234.30
Purchase #7	$168.27	11.560%	$187.722	$187.72	$187.70	$187.70
7 purchase totals =	$1,028.47		$1,128.4804	$1,128.49	$1,128.45	$1,128.50