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	$100.65	11.111%	$111.8332	$111.83	$111.85	$111.80
Purchase #2	$216.72	10.677%	$239.8592	$239.86	$239.85	$239.90
Purchase #3	$204.31	8.603%	$221.8868	$221.89	$221.90	$221.90
Purchase #4	$152.51	4.102%	$158.766	$158.77	$158.75	$158.80
Purchase #5	$211.68	10.266%	$233.4111	$233.41	$233.40	$233.40
Purchase #6	$109.86	10.431%	$121.3195	$121.32	$121.30	$121.30
Purchase #7	$156.56	5.553%	$165.2538	$165.25	$165.25	$165.30
7 purchase totals =	$1,152.29		$1,252.3296	$1,252.33	$1,252.30	$1,252.40