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	$130.33	12.650%	$146.8167	$146.82	$146.80	$146.80
Purchase #2	$219.38	3.550%	$227.168	$227.17	$227.15	$227.20
Purchase #3	$216.44	9.810%	$237.6728	$237.67	$237.65	$237.70
Purchase #4	$133.51	13.492%	$151.5232	$151.52	$151.50	$151.50
Purchase #5	$42.94	4.341%	$44.804	$44.80	$44.80	$44.80
Purchase #6	$35.82	13.855%	$40.7829	$40.78	$40.80	$40.80
Purchase #7	$114.55	11.231%	$127.4151	$127.42	$127.40	$127.40
7 purchase totals =	$892.97		$976.1827	$976.18	$976.10	$976.20