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	$218.88	3.817%	$227.2346	$227.23	$227.25	$227.20
Purchase #2	$108.34	7.205%	$116.1459	$116.15	$116.15	$116.10
Purchase #3	$167.55	3.251%	$172.9971	$173.00	$173.00	$173.00
Purchase #4	$53.25	11.723%	$59.4925	$59.49	$59.50	$59.50
Purchase #5	$59.75	12.739%	$67.3616	$67.36	$67.35	$67.40
Purchase #6	$30.69	6.246%	$32.6069	$32.61	$32.60	$32.60
Purchase #7	$101.52	10.707%	$112.3897	$112.39	$112.40	$112.40
7 purchase totals =	$739.98		$788.2283	$788.23	$788.25	$788.20