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	$50.67	6.733%	$54.0816	$54.08	$54.10	$54.10
Purchase #2	$12.88	11.247%	$14.3286	$14.33	$14.35	$14.30
Purchase #3	$231.44	10.790%	$256.4124	$256.41	$256.40	$256.40
Purchase #4	$37.75	12.714%	$42.5495	$42.55	$42.55	$42.50
Purchase #5	$66.72	9.784%	$73.2479	$73.25	$73.25	$73.20
Purchase #6	$172.31	12.454%	$193.7695	$193.77	$193.75	$193.80
Purchase #7	$184.56	4.525%	$192.9113	$192.91	$192.90	$192.90
7 purchase totals =	$756.33		$827.3008	$827.30	$827.30	$827.20