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	$206.78	8.627%	$224.6189	$224.62	$224.60	$224.60
Purchase #2	$173.90	12.276%	$195.248	$195.25	$195.25	$195.20
Purchase #3	$127.55	4.594%	$133.4096	$133.41	$133.40	$133.40
Purchase #4	$167.30	6.751%	$178.5944	$178.59	$178.60	$178.60
Purchase #5	$59.51	3.281%	$61.4625	$61.46	$61.45	$61.50
Purchase #6	$92.93	8.660%	$100.9777	$100.98	$101.00	$101.00
Purchase #7	$243.42	6.177%	$258.4561	$258.46	$258.45	$258.50
7 purchase totals =	$1,071.39		$1,152.7672	$1,152.77	$1,152.75	$1,152.80