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	$237.55	5.415%	$250.4133	$250.41	$250.40	$250.40
Purchase #2	$208.68	6.698%	$222.6574	$222.66	$222.65	$222.70
Purchase #3	$153.35	3.366%	$158.5118	$158.51	$158.50	$158.50
Purchase #4	$168.61	13.731%	$191.7618	$191.76	$191.75	$191.80
Purchase #5	$32.90	11.120%	$36.5585	$36.56	$36.55	$36.60
Purchase #6	$157.80	9.618%	$172.9772	$172.98	$173.00	$173.00
Purchase #7	$50.54	8.340%	$54.755	$54.76	$54.75	$54.80
7 purchase totals =	$1,009.43		$1,087.6350	$1,087.64	$1,087.60	$1,087.80