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	$68.97	10.205%	$76.0084	$76.01	$76.00	$76.00
Purchase #2	$98.75	12.254%	$110.8508	$110.85	$110.85	$110.90
Purchase #3	$34.65	7.429%	$37.2241	$37.22	$37.20	$37.20
Purchase #4	$127.29	13.343%	$144.2743	$144.27	$144.25	$144.30
Purchase #5	$189.44	3.753%	$196.5497	$196.55	$196.55	$196.50
Purchase #6	$35.39	5.286%	$37.2607	$37.26	$37.25	$37.30
Purchase #7	$17.57	13.703%	$19.9776	$19.98	$20.00	$20.00
7 purchase totals =	$572.06		$622.1456	$622.14	$622.10	$622.20