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	$186.71	7.449%	$200.618	$200.62	$200.60	$200.60
Purchase #2	$16.91	4.272%	$17.6324	$17.63	$17.65	$17.60
Purchase #3	$108.45	13.826%	$123.4443	$123.44	$123.45	$123.40
Purchase #4	$89.66	7.430%	$96.3217	$96.32	$96.30	$96.30
Purchase #5	$88.43	3.400%	$91.4366	$91.44	$91.45	$91.40
Purchase #6	$179.59	11.714%	$200.6272	$200.63	$200.65	$200.60
Purchase #7	$172.72	10.305%	$190.5188	$190.52	$190.50	$190.50
7 purchase totals =	$842.47		$920.5990	$920.60	$920.60	$920.40