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	$150.44	3.812%	$156.1748	$156.17	$156.15	$156.20
Purchase #2	$135.85	8.152%	$146.9245	$146.92	$146.90	$146.90
Purchase #3	$224.82	13.207%	$254.512	$254.51	$254.50	$254.50
Purchase #4	$93.97	6.705%	$100.2707	$100.27	$100.25	$100.30
Purchase #5	$123.34	3.463%	$127.6113	$127.61	$127.60	$127.60
Purchase #6	$221.85	6.690%	$236.6918	$236.69	$236.70	$236.70
Purchase #7	$173.88	10.755%	$192.5808	$192.58	$192.60	$192.60
7 purchase totals =	$1,124.15		$1,214.7659	$1,214.75	$1,214.70	$1,214.80