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	$127.77	13.594%	$145.1391	$145.14	$145.15	$145.10
Purchase #2	$141.37	4.322%	$147.48	$147.48	$147.50	$147.50
Purchase #3	$218.59	9.324%	$238.9713	$238.97	$238.95	$239.00
Purchase #4	$144.83	11.256%	$161.1321	$161.13	$161.15	$161.10
Purchase #5	$100.53	3.769%	$104.319	$104.32	$104.30	$104.30
Purchase #6	$135.37	13.118%	$153.1278	$153.13	$153.15	$153.10
Purchase #7	$167.55	11.361%	$186.5854	$186.59	$186.60	$186.60
7 purchase totals =	$1,036.01		$1,136.7547	$1,136.76	$1,136.80	$1,136.70