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	$114.54	8.360%	$124.1155	$124.12	$124.10	$124.10
Purchase #2	$219.57	3.552%	$227.3691	$227.37	$227.35	$227.40
Purchase #3	$186.57	10.153%	$205.5125	$205.51	$205.50	$205.50
Purchase #4	$93.38	7.628%	$100.503	$100.50	$100.50	$100.50
Purchase #5	$9.64	13.267%	$10.9189	$10.92	$10.90	$10.90
Purchase #6	$145.57	5.513%	$153.5953	$153.60	$153.60	$153.60
Purchase #7	$142.38	6.182%	$151.1819	$151.18	$151.20	$151.20
7 purchase totals =	$911.65		$973.1962	$973.20	$973.15	$973.20