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	$101.54	11.448%	$113.1643	$113.16	$113.15	$113.20
Purchase #2	$54.72	3.278%	$56.5137	$56.51	$56.50	$56.50
Purchase #3	$85.88	5.346%	$90.4711	$90.47	$90.45	$90.50
Purchase #4	$31.94	13.260%	$36.1752	$36.18	$36.20	$36.20
Purchase #5	$157.60	6.313%	$167.5493	$167.55	$167.55	$167.50
Purchase #6	$78.80	12.277%	$88.4743	$88.47	$88.45	$88.50
Purchase #7	$151.52	5.537%	$159.9097	$159.91	$159.90	$159.90
7 purchase totals =	$662.00		$712.2576	$712.25	$712.20	$712.30