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	$157.97	11.153%	$175.5884	$175.59	$175.60	$175.60
Purchase #2	$64.75	13.417%	$73.4375	$73.44	$73.45	$73.40
Purchase #3	$128.68	12.575%	$144.8615	$144.86	$144.85	$144.90
Purchase #4	$73.25	13.852%	$83.3966	$83.40	$83.40	$83.40
Purchase #5	$250.80	13.392%	$284.3871	$284.39	$284.40	$284.40
Purchase #6	$96.74	4.326%	$100.925	$100.93	$100.95	$100.90
Purchase #7	$52.54	3.110%	$54.174	$54.17	$54.15	$54.20
7 purchase totals =	$824.73		$916.7701	$916.78	$916.80	$916.80