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	$171.32	11.146%	$190.4153	$190.42	$190.40	$190.40
Purchase #2	$5.92	10.297%	$6.5296	$6.53	$6.55	$6.50
Purchase #3	$110.50	7.621%	$118.9212	$118.92	$118.90	$118.90
Purchase #4	$244.66	13.870%	$278.5943	$278.59	$278.60	$278.60
Purchase #5	$28.30	4.365%	$29.5353	$29.54	$29.55	$29.50
Purchase #6	$23.81	10.186%	$26.2353	$26.24	$26.25	$26.20
Purchase #7	$37.61	12.677%	$42.3778	$42.38	$42.40	$42.40
7 purchase totals =	$622.12		$692.6088	$692.62	$692.65	$692.50