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	$216.67	13.843%	$246.6636	$246.66	$246.65	$246.70
Purchase #2	$89.67	11.322%	$99.8224	$99.82	$99.80	$99.80
Purchase #3	$219.27	10.707%	$242.7472	$242.75	$242.75	$242.70
Purchase #4	$105.52	10.519%	$116.6196	$116.62	$116.60	$116.60
Purchase #5	$189.54	11.271%	$210.9031	$210.90	$210.90	$210.90
Purchase #6	$99.40	6.468%	$105.8292	$105.83	$105.85	$105.80
Purchase #7	$107.84	3.640%	$111.7654	$111.77	$111.75	$111.80
7 purchase totals =	$1,027.91		$1,134.3505	$1,134.35	$1,134.30	$1,134.30