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	$70.40	8.609%	$76.4607	$76.46	$76.45	$76.50
Purchase #2	$165.69	4.479%	$173.1113	$173.11	$173.10	$173.10
Purchase #3	$176.63	13.191%	$199.9293	$199.93	$199.95	$199.90
Purchase #4	$95.94	7.823%	$103.4454	$103.45	$103.45	$103.40
Purchase #5	$60.66	9.466%	$66.4021	$66.40	$66.40	$66.40
Purchase #6	$216.46	11.621%	$241.6148	$241.61	$241.60	$241.60
Purchase #7	$218.64	9.412%	$239.2184	$239.22	$239.20	$239.20
7 purchase totals =	$1,004.42		$1,100.1820	$1,100.18	$1,100.15	$1,100.10