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	$151.78	7.742%	$163.5308	$163.53	$163.55	$163.50
Purchase #2	$173.39	9.809%	$190.3978	$190.40	$190.40	$190.40
Purchase #3	$192.80	7.820%	$207.877	$207.88	$207.90	$207.90
Purchase #4	$29.25	11.502%	$32.6143	$32.61	$32.60	$32.60
Purchase #5	$102.77	8.418%	$111.4212	$111.42	$111.40	$111.40
Purchase #6	$246.67	11.727%	$275.597	$275.60	$275.60	$275.60
Purchase #7	$149.82	11.331%	$166.7961	$166.80	$166.80	$166.80
7 purchase totals =	$1,046.48		$1,148.2342	$1,148.24	$1,148.25	$1,148.20