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	$193.75	11.388%	$215.8143	$215.81	$215.80	$215.80
Purchase #2	$98.99	4.220%	$103.1674	$103.17	$103.15	$103.20
Purchase #3	$131.82	13.104%	$149.0937	$149.09	$149.10	$149.10
Purchase #4	$106.33	9.754%	$116.7014	$116.70	$116.70	$116.70
Purchase #5	$116.38	9.336%	$127.2452	$127.25	$127.25	$127.20
Purchase #6	$203.61	12.117%	$228.2814	$228.28	$228.30	$228.30
Purchase #7	$172.96	13.504%	$196.3165	$196.32	$196.30	$196.30
7 purchase totals =	$1,023.84		$1,136.6199	$1,136.62	$1,136.60	$1,136.60