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	$57.82	9.803%	$63.4881	$63.49	$63.50	$63.50
Purchase #2	$42.57	13.641%	$48.377	$48.38	$48.40	$48.40
Purchase #3	$175.50	13.728%	$199.5926	$199.59	$199.60	$199.60
Purchase #4	$74.56	4.136%	$77.6438	$77.64	$77.65	$77.60
Purchase #5	$66.38	3.865%	$68.9456	$68.95	$68.95	$68.90
Purchase #6	$184.69	6.466%	$196.6321	$196.63	$196.65	$196.60
Purchase #7	$110.72	8.117%	$119.7071	$119.71	$119.70	$119.70
7 purchase totals =	$712.24		$774.3863	$774.39	$774.45	$774.30