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	$102.74	11.268%	$114.3167	$114.32	$114.30	$114.30
Purchase #2	$221.31	13.844%	$251.9482	$251.95	$251.95	$251.90
Purchase #3	$152.41	6.454%	$162.2465	$162.25	$162.25	$162.20
Purchase #4	$113.27	12.792%	$127.7595	$127.76	$127.75	$127.80
Purchase #5	$135.71	8.621%	$147.4096	$147.41	$147.40	$147.40
Purchase #6	$47.91	10.643%	$53.0091	$53.01	$53.00	$53.00
Purchase #7	$185.87	13.852%	$211.6167	$211.62	$211.60	$211.60
7 purchase totals =	$959.22		$1,068.3063	$1,068.32	$1,068.25	$1,068.20