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	$128.76	13.427%	$146.0486	$146.05	$146.05	$146.00
Purchase #2	$51.27	4.572%	$53.6141	$53.61	$53.60	$53.60
Purchase #3	$76.59	11.452%	$85.3611	$85.36	$85.35	$85.40
Purchase #4	$173.93	7.317%	$186.6565	$186.66	$186.65	$186.70
Purchase #5	$80.96	10.492%	$89.4543	$89.45	$89.45	$89.50
Purchase #6	$165.61	12.433%	$186.2003	$186.20	$186.20	$186.20
Purchase #7	$13.75	9.723%	$15.0869	$15.09	$15.10	$15.10
7 purchase totals =	$690.87		$762.4218	$762.42	$762.40	$762.50