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	$230.98	4.569%	$241.5335	$241.53	$241.55	$241.50
Purchase #2	$183.27	12.699%	$206.5435	$206.54	$206.55	$206.50
Purchase #3	$99.84	8.496%	$108.3224	$108.32	$108.30	$108.30
Purchase #4	$40.70	13.760%	$46.3003	$46.30	$46.30	$46.30
Purchase #5	$40.67	4.220%	$42.3863	$42.39	$42.40	$42.40
Purchase #6	$61.90	5.753%	$65.4611	$65.46	$65.45	$65.50
Purchase #7	$21.49	5.247%	$22.6176	$22.62	$22.60	$22.60
7 purchase totals =	$678.85		$733.1647	$733.16	$733.15	$733.10