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	$149.78	9.551%	$164.0855	$164.09	$164.10	$164.10
Purchase #2	$165.67	4.873%	$173.7431	$173.74	$173.75	$173.70
Purchase #3	$62.29	5.485%	$65.7066	$65.71	$65.70	$65.70
Purchase #4	$173.27	5.107%	$182.1189	$182.12	$182.10	$182.10
Purchase #5	$127.45	7.259%	$136.7016	$136.70	$136.70	$136.70
Purchase #6	$70.50	10.731%	$78.0654	$78.07	$78.05	$78.10
Purchase #7	$105.58	6.648%	$112.599	$112.60	$112.60	$112.60
7 purchase totals =	$854.54		$913.0201	$913.03	$913.00	$913.00