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	$104.64	6.631%	$111.5787	$111.58	$111.60	$111.60
Purchase #2	$84.88	4.441%	$88.6495	$88.65	$88.65	$88.60
Purchase #3	$181.53	11.183%	$201.8305	$201.83	$201.85	$201.80
Purchase #4	$114.31	11.308%	$127.2362	$127.24	$127.25	$127.20
Purchase #5	$74.92	6.146%	$79.5246	$79.52	$79.50	$79.50
Purchase #6	$129.83	12.855%	$146.5196	$146.52	$146.50	$146.50
Purchase #7	$159.93	10.638%	$176.9434	$176.94	$176.95	$176.90
7 purchase totals =	$850.04		$932.2825	$932.28	$932.30	$932.10