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	$151.78	3.142%	$156.5489	$156.55	$156.55	$156.50
Purchase #2	$86.29	3.279%	$89.1194	$89.12	$89.10	$89.10
Purchase #3	$127.28	4.114%	$132.5163	$132.52	$132.50	$132.50
Purchase #4	$93.26	7.579%	$100.3282	$100.33	$100.35	$100.30
Purchase #5	$84.70	4.536%	$88.542	$88.54	$88.55	$88.50
Purchase #6	$160.31	8.336%	$173.6734	$173.67	$173.65	$173.70
Purchase #7	$57.78	4.548%	$60.4078	$60.41	$60.40	$60.40
7 purchase totals =	$761.40		$801.1360	$801.14	$801.10	$801.00