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	$79.74	12.402%	$89.6294	$89.63	$89.65	$89.60
Purchase #2	$128.58	8.544%	$139.5659	$139.57	$139.55	$139.60
Purchase #3	$183.60	8.583%	$199.3584	$199.36	$199.35	$199.40
Purchase #4	$230.87	9.427%	$252.6341	$252.63	$252.65	$252.60
Purchase #5	$144.89	5.576%	$152.9691	$152.97	$152.95	$153.00
Purchase #6	$105.69	5.380%	$111.3761	$111.38	$111.40	$111.40
Purchase #7	$204.30	11.176%	$227.1326	$227.13	$227.15	$227.10
7 purchase totals =	$1,077.67		$1,172.6656	$1,172.67	$1,172.70	$1,172.70