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	$206.57	4.712%	$216.3036	$216.30	$216.30	$216.30
Purchase #2	$67.81	5.695%	$71.6718	$71.67	$71.65	$71.70
Purchase #3	$146.98	12.370%	$165.1614	$165.16	$165.15	$165.20
Purchase #4	$163.72	5.249%	$172.3137	$172.31	$172.30	$172.30
Purchase #5	$190.81	3.108%	$196.7404	$196.74	$196.75	$196.70
Purchase #6	$39.73	7.238%	$42.6057	$42.61	$42.60	$42.60
Purchase #7	$82.41	6.201%	$87.5202	$87.52	$87.50	$87.50
7 purchase totals =	$898.03		$952.3168	$952.31	$952.25	$952.30