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	$155.59	7.332%	$166.9979	$167.00	$167.00	$167.00
Purchase #2	$137.72	4.176%	$143.4712	$143.47	$143.45	$143.50
Purchase #3	$36.52	3.579%	$37.8271	$37.83	$37.85	$37.80
Purchase #4	$139.55	4.789%	$146.233	$146.23	$146.25	$146.20
Purchase #5	$69.62	4.542%	$72.7821	$72.78	$72.80	$72.80
Purchase #6	$66.71	5.166%	$70.1562	$70.16	$70.15	$70.20
Purchase #7	$183.81	13.571%	$208.7549	$208.75	$208.75	$208.80
7 purchase totals =	$789.52		$846.2224	$846.22	$846.25	$846.30