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	$164.91	4.644%	$172.5684	$172.57	$172.55	$172.60
Purchase #2	$139.53	13.414%	$158.2466	$158.25	$158.25	$158.20
Purchase #3	$120.50	5.475%	$127.0974	$127.10	$127.10	$127.10
Purchase #4	$224.81	10.433%	$248.2644	$248.26	$248.25	$248.30
Purchase #5	$101.87	3.222%	$105.1523	$105.15	$105.15	$105.20
Purchase #6	$103.82	6.469%	$110.5361	$110.54	$110.55	$110.50
Purchase #7	$217.38	5.640%	$229.6402	$229.64	$229.65	$229.60
7 purchase totals =	$1,072.82		$1,151.5054	$1,151.51	$1,151.50	$1,151.50