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	$163.54	5.726%	$172.9043	$172.90	$172.90	$172.90
Purchase #2	$218.46	3.418%	$225.927	$225.93	$225.95	$225.90
Purchase #3	$223.66	7.849%	$241.2151	$241.22	$241.20	$241.20
Purchase #4	$74.84	10.177%	$82.4565	$82.46	$82.45	$82.50
Purchase #5	$65.56	7.162%	$70.2554	$70.26	$70.25	$70.30
Purchase #6	$64.97	9.758%	$71.3098	$71.31	$71.30	$71.30
Purchase #7	$219.95	6.129%	$233.4307	$233.43	$233.45	$233.40
7 purchase totals =	$1,030.98		$1,097.4988	$1,097.51	$1,097.50	$1,097.50