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	$54.42	9.363%	$59.5153	$59.52	$59.50	$59.50
Purchase #2	$225.45	11.770%	$251.9855	$251.99	$252.00	$252.00
Purchase #3	$26.30	7.486%	$28.2688	$28.27	$28.25	$28.30
Purchase #4	$129.66	10.392%	$143.1343	$143.13	$143.15	$143.10
Purchase #5	$121.42	13.247%	$137.5045	$137.50	$137.50	$137.50
Purchase #6	$185.87	6.305%	$197.5891	$197.59	$197.60	$197.60
Purchase #7	$206.77	10.801%	$229.1032	$229.10	$229.10	$229.10
7 purchase totals =	$949.89		$1,047.1007	$1,047.10	$1,047.10	$1,047.10