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	$56.59	6.828%	$60.454	$60.45	$60.45	$60.50
Purchase #2	$109.98	3.635%	$113.9778	$113.98	$114.00	$114.00
Purchase #3	$119.55	6.298%	$127.0793	$127.08	$127.10	$127.10
Purchase #4	$92.68	4.128%	$96.5058	$96.51	$96.50	$96.50
Purchase #5	$174.42	10.152%	$192.1271	$192.13	$192.15	$192.10
Purchase #6	$37.32	8.318%	$40.4243	$40.42	$40.40	$40.40
Purchase #7	$149.96	4.840%	$157.2181	$157.22	$157.20	$157.20
7 purchase totals =	$740.50		$787.7864	$787.79	$787.80	$787.80