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	$134.65	3.685%	$139.6119	$139.61	$139.60	$139.60
Purchase #2	$98.77	13.374%	$111.9795	$111.98	$112.00	$112.00
Purchase #3	$33.60	4.611%	$35.1493	$35.15	$35.15	$35.10
Purchase #4	$87.81	6.741%	$93.7293	$93.73	$93.75	$93.70
Purchase #5	$150.38	6.253%	$159.7833	$159.78	$159.80	$159.80
Purchase #6	$41.27	5.251%	$43.4371	$43.44	$43.45	$43.40
Purchase #7	$167.33	3.401%	$173.0209	$173.02	$173.00	$173.00
7 purchase totals =	$713.81		$756.7113	$756.71	$756.75	$756.60