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	$105.77	5.347%	$111.4255	$111.43	$111.45	$111.40
Purchase #2	$40.41	5.127%	$42.4818	$42.48	$42.50	$42.50
Purchase #3	$78.42	12.711%	$88.388	$88.39	$88.40	$88.40
Purchase #4	$120.48	11.653%	$134.5195	$134.52	$134.50	$134.50
Purchase #5	$149.83	10.549%	$165.6356	$165.64	$165.65	$165.60
Purchase #6	$28.65	13.842%	$32.6157	$32.62	$32.60	$32.60
Purchase #7	$191.36	4.390%	$199.7607	$199.76	$199.75	$199.80
7 purchase totals =	$714.92		$774.8268	$774.84	$774.85	$774.80