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	$67.36	10.619%	$74.513	$74.51	$74.50	$74.50
Purchase #2	$134.98	5.209%	$142.0111	$142.01	$142.00	$142.00
Purchase #3	$35.27	12.243%	$39.5881	$39.59	$39.60	$39.60
Purchase #4	$239.66	3.861%	$248.9133	$248.91	$248.90	$248.90
Purchase #5	$129.92	6.459%	$138.3115	$138.31	$138.30	$138.30
Purchase #6	$154.89	11.544%	$172.7705	$172.77	$172.75	$172.80
Purchase #7	$114.86	10.625%	$127.0639	$127.06	$127.05	$127.10
7 purchase totals =	$876.94		$943.1714	$943.16	$943.10	$943.20