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	$208.70	10.750%	$231.1353	$231.14	$231.15	$231.10
Purchase #2	$76.46	12.365%	$85.9143	$85.91	$85.90	$85.90
Purchase #3	$161.98	7.140%	$173.5454	$173.55	$173.55	$173.50
Purchase #4	$161.91	10.774%	$179.3542	$179.35	$179.35	$179.40
Purchase #5	$77.95	9.206%	$85.1261	$85.13	$85.15	$85.10
Purchase #6	$101.59	3.412%	$105.0563	$105.06	$105.05	$105.10
Purchase #7	$122.30	4.204%	$127.4415	$127.44	$127.45	$127.40
7 purchase totals =	$910.89		$987.5731	$987.58	$987.60	$987.50