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	$192.40	11.496%	$214.5183	$214.52	$214.50	$214.50
Purchase #2	$88.43	8.584%	$96.0208	$96.02	$96.00	$96.00
Purchase #3	$65.73	13.567%	$74.6476	$74.65	$74.65	$74.60
Purchase #4	$101.48	3.752%	$105.2875	$105.29	$105.30	$105.30
Purchase #5	$119.83	11.730%	$133.8861	$133.89	$133.90	$133.90
Purchase #6	$79.95	3.129%	$82.4516	$82.45	$82.45	$82.50
Purchase #7	$132.39	5.834%	$140.1136	$140.11	$140.10	$140.10
7 purchase totals =	$780.21		$846.9255	$846.93	$846.90	$846.90