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	$234.53	7.491%	$252.0986	$252.10	$252.10	$252.10
Purchase #2	$19.60	5.788%	$20.7344	$20.73	$20.75	$20.70
Purchase #3	$29.88	11.188%	$33.223	$33.22	$33.20	$33.20
Purchase #4	$113.46	13.352%	$128.6092	$128.61	$128.60	$128.60
Purchase #5	$217.90	3.583%	$225.7074	$225.71	$225.70	$225.70
Purchase #6	$238.58	7.238%	$255.8484	$255.85	$255.85	$255.80
Purchase #7	$91.40	11.166%	$101.6057	$101.61	$101.60	$101.60
7 purchase totals =	$945.35		$1,017.8267	$1,017.83	$1,017.80	$1,017.70