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	$147.71	6.282%	$156.9891	$156.99	$157.00	$157.00
Purchase #2	$186.49	5.267%	$196.3124	$196.31	$196.30	$196.30
Purchase #3	$120.70	5.461%	$127.2914	$127.29	$127.30	$127.30
Purchase #4	$114.83	6.783%	$122.6189	$122.62	$122.60	$122.60
Purchase #5	$158.81	9.276%	$173.5412	$173.54	$173.55	$173.50
Purchase #6	$121.72	10.180%	$134.1111	$134.11	$134.10	$134.10
Purchase #7	$59.97	9.533%	$65.6869	$65.69	$65.70	$65.70
7 purchase totals =	$910.23		$976.5510	$976.55	$976.55	$976.50