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	$214.58	7.320%	$230.2873	$230.29	$230.30	$230.30
Purchase #2	$187.89	6.442%	$199.9939	$199.99	$200.00	$200.00
Purchase #3	$26.43	10.226%	$29.1327	$29.13	$29.15	$29.10
Purchase #4	$148.75	5.607%	$157.0904	$157.09	$157.10	$157.10
Purchase #5	$111.94	4.126%	$116.5586	$116.56	$116.55	$116.60
Purchase #6	$142.85	13.636%	$162.329	$162.33	$162.35	$162.30
Purchase #7	$77.85	6.535%	$82.9375	$82.94	$82.95	$82.90
7 purchase totals =	$910.29		$978.3294	$978.33	$978.40	$978.30