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	$98.60	7.286%	$105.784	$105.78	$105.80	$105.80
Purchase #2	$117.57	8.595%	$127.6751	$127.68	$127.70	$127.70
Purchase #3	$88.95	11.873%	$99.511	$99.51	$99.50	$99.50
Purchase #4	$134.28	6.560%	$143.0888	$143.09	$143.10	$143.10
Purchase #5	$173.37	10.587%	$191.7247	$191.72	$191.70	$191.70
Purchase #6	$95.32	6.375%	$101.3967	$101.40	$101.40	$101.40
Purchase #7	$184.30	4.218%	$192.0738	$192.07	$192.05	$192.10
7 purchase totals =	$892.39		$961.2541	$961.25	$961.25	$961.30