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	$175.80	8.207%	$190.2279	$190.23	$190.25	$190.20
Purchase #2	$157.51	10.369%	$173.8422	$173.84	$173.85	$173.80
Purchase #3	$105.48	5.721%	$111.5145	$111.51	$111.50	$111.50
Purchase #4	$65.73	7.246%	$70.4928	$70.49	$70.50	$70.50
Purchase #5	$151.54	8.113%	$163.8344	$163.83	$163.85	$163.80
Purchase #6	$78.32	7.133%	$83.9066	$83.91	$83.90	$83.90
Purchase #7	$200.56	7.575%	$215.7524	$215.75	$215.75	$215.80
7 purchase totals =	$934.94		$1,009.5708	$1,009.56	$1,009.60	$1,009.50