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	$166.89	3.801%	$173.2335	$173.23	$173.25	$173.20
Purchase #2	$126.50	11.837%	$141.4738	$141.47	$141.45	$141.50
Purchase #3	$113.88	12.515%	$128.1321	$128.13	$128.15	$128.10
Purchase #4	$240.71	5.630%	$254.262	$254.26	$254.25	$254.30
Purchase #5	$111.64	6.333%	$118.7102	$118.71	$118.70	$118.70
Purchase #6	$178.32	3.527%	$184.6093	$184.61	$184.60	$184.60
Purchase #7	$157.85	4.700%	$165.269	$165.27	$165.25	$165.30
7 purchase totals =	$1,095.79		$1,165.6899	$1,165.68	$1,165.65	$1,165.70