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	$150.73	9.284%	$164.7238	$164.72	$164.70	$164.70
Purchase #2	$89.54	3.428%	$92.6094	$92.61	$92.60	$92.60
Purchase #3	$60.98	5.219%	$64.1625	$64.16	$64.15	$64.20
Purchase #4	$35.75	9.785%	$39.2481	$39.25	$39.25	$39.20
Purchase #5	$57.92	6.626%	$61.7578	$61.76	$61.75	$61.80
Purchase #6	$35.97	10.185%	$39.6335	$39.63	$39.65	$39.60
Purchase #7	$244.83	4.792%	$256.5623	$256.56	$256.55	$256.60
7 purchase totals =	$675.72		$718.6974	$718.69	$718.65	$718.70