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	$146.73	13.219%	$166.1262	$166.13	$166.15	$166.10
Purchase #2	$123.25	3.345%	$127.3727	$127.37	$127.35	$127.40
Purchase #3	$129.81	10.744%	$143.7568	$143.76	$143.75	$143.80
Purchase #4	$13.50	6.399%	$14.3639	$14.36	$14.35	$14.40
Purchase #5	$73.27	10.767%	$81.159	$81.16	$81.15	$81.20
Purchase #6	$37.73	3.715%	$39.1317	$39.13	$39.15	$39.10
Purchase #7	$152.47	8.611%	$165.5992	$165.60	$165.60	$165.60
7 purchase totals =	$676.76		$737.5095	$737.51	$737.50	$737.60