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	$189.71	11.306%	$211.1586	$211.16	$211.15	$211.20
Purchase #2	$226.56	6.585%	$241.479	$241.48	$241.50	$241.50
Purchase #3	$59.38	13.333%	$67.2971	$67.30	$67.30	$67.30
Purchase #4	$53.73	12.621%	$60.5113	$60.51	$60.50	$60.50
Purchase #5	$163.39	6.320%	$173.7162	$173.72	$173.70	$173.70
Purchase #6	$139.59	7.791%	$150.4655	$150.47	$150.45	$150.50
Purchase #7	$172.35	3.422%	$178.2478	$178.25	$178.25	$178.20
7 purchase totals =	$1,004.71		$1,082.8755	$1,082.89	$1,082.85	$1,082.90