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	$224.31	12.586%	$252.5417	$252.54	$252.55	$252.50
Purchase #2	$164.79	13.759%	$187.4635	$187.46	$187.45	$187.50
Purchase #3	$199.55	6.525%	$212.5706	$212.57	$212.55	$212.60
Purchase #4	$137.62	6.375%	$146.3933	$146.39	$146.40	$146.40
Purchase #5	$85.50	3.253%	$88.2813	$88.28	$88.30	$88.30
Purchase #6	$85.82	10.133%	$94.5161	$94.52	$94.50	$94.50
Purchase #7	$205.89	4.174%	$214.4838	$214.48	$214.50	$214.50
7 purchase totals =	$1,103.48		$1,196.2503	$1,196.24	$1,196.25	$1,196.30