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	$249.88	5.113%	$262.6564	$262.66	$262.65	$262.70
Purchase #2	$141.41	8.177%	$152.9731	$152.97	$152.95	$153.00
Purchase #3	$9.64	3.251%	$9.9534	$9.95	$9.95	$10.00
Purchase #4	$72.72	6.706%	$77.5966	$77.60	$77.60	$77.60
Purchase #5	$64.90	11.147%	$72.1344	$72.13	$72.15	$72.10
Purchase #6	$48.37	8.840%	$52.6459	$52.65	$52.65	$52.60
Purchase #7	$162.77	6.217%	$172.8894	$172.89	$172.90	$172.90
7 purchase totals =	$749.69		$800.8492	$800.85	$800.85	$800.90