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	$183.74	13.261%	$208.1058	$208.11	$208.10	$208.10
Purchase #2	$229.52	11.475%	$255.8574	$255.86	$255.85	$255.90
Purchase #3	$172.48	12.747%	$194.466	$194.47	$194.45	$194.50
Purchase #4	$103.86	13.523%	$117.905	$117.91	$117.90	$117.90
Purchase #5	$17.75	10.645%	$19.6395	$19.64	$19.65	$19.60
Purchase #6	$153.84	7.490%	$165.3626	$165.36	$165.35	$165.40
Purchase #7	$134.46	7.222%	$144.1707	$144.17	$144.15	$144.20
7 purchase totals =	$995.65		$1,105.5070	$1,105.52	$1,105.45	$1,105.60