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	$50.98	10.131%	$56.1448	$56.14	$56.15	$56.10
Purchase #2	$75.77	13.635%	$86.1012	$86.10	$86.10	$86.10
Purchase #3	$145.43	6.323%	$154.6255	$154.63	$154.65	$154.60
Purchase #4	$82.44	4.820%	$86.4136	$86.41	$86.40	$86.40
Purchase #5	$89.63	10.598%	$99.129	$99.13	$99.15	$99.10
Purchase #6	$240.99	3.631%	$249.7403	$249.74	$249.75	$249.70
Purchase #7	$32.49	5.631%	$34.3195	$34.32	$34.30	$34.30
7 purchase totals =	$717.73		$766.4739	$766.47	$766.50	$766.30