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	$10.58	6.690%	$11.2878	$11.29	$11.30	$11.30
Purchase #2	$114.73	3.333%	$118.554	$118.55	$118.55	$118.60
Purchase #3	$183.90	6.729%	$196.2746	$196.27	$196.25	$196.30
Purchase #4	$103.80	7.580%	$111.668	$111.67	$111.65	$111.70
Purchase #5	$228.33	13.137%	$258.3257	$258.33	$258.35	$258.30
Purchase #6	$185.61	11.420%	$206.8067	$206.81	$206.80	$206.80
Purchase #7	$132.43	5.163%	$139.2674	$139.27	$139.25	$139.30
7 purchase totals =	$959.38		$1,042.1842	$1,042.19	$1,042.15	$1,042.30