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	$151.40	9.561%	$165.8754	$165.88	$165.90	$165.90
Purchase #2	$147.58	13.334%	$167.2583	$167.26	$167.25	$167.30
Purchase #3	$216.84	5.680%	$229.1565	$229.16	$229.15	$229.20
Purchase #4	$75.38	11.245%	$83.8565	$83.86	$83.85	$83.90
Purchase #5	$190.27	4.251%	$198.3584	$198.36	$198.35	$198.40
Purchase #6	$239.73	8.368%	$259.7906	$259.79	$259.80	$259.80
Purchase #7	$151.47	4.721%	$158.6209	$158.62	$158.60	$158.60
7 purchase totals =	$1,172.67		$1,262.9166	$1,262.93	$1,262.90	$1,263.10