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	$149.83	11.652%	$167.2882	$167.29	$167.30	$167.30
Purchase #2	$152.60	13.510%	$173.2163	$173.22	$173.20	$173.20
Purchase #3	$250.60	5.407%	$264.1499	$264.15	$264.15	$264.10
Purchase #4	$164.47	13.279%	$186.31	$186.31	$186.30	$186.30
Purchase #5	$75.75	6.202%	$80.448	$80.45	$80.45	$80.40
Purchase #6	$13.77	4.684%	$14.415	$14.42	$14.40	$14.40
Purchase #7	$191.38	13.680%	$217.5608	$217.56	$217.55	$217.60
7 purchase totals =	$998.40		$1,103.3882	$1,103.40	$1,103.35	$1,103.30