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	$59.57	6.726%	$63.5767	$63.58	$63.60	$63.60
Purchase #2	$90.69	10.833%	$100.5144	$100.51	$100.50	$100.50
Purchase #3	$134.51	12.476%	$151.2915	$151.29	$151.30	$151.30
Purchase #4	$28.36	11.578%	$31.6435	$31.64	$31.65	$31.60
Purchase #5	$75.35	3.860%	$78.2585	$78.26	$78.25	$78.30
Purchase #6	$180.80	5.298%	$190.3788	$190.38	$190.40	$190.40
Purchase #7	$55.97	10.406%	$61.7942	$61.79	$61.80	$61.80
7 purchase totals =	$625.25		$677.4576	$677.45	$677.50	$677.50