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	$147.40	12.564%	$165.9193	$165.92	$165.90	$165.90
Purchase #2	$131.30	4.548%	$137.2715	$137.27	$137.25	$137.30
Purchase #3	$18.65	4.809%	$19.5469	$19.55	$19.55	$19.50
Purchase #4	$134.66	8.136%	$145.6159	$145.62	$145.60	$145.60
Purchase #5	$227.68	6.408%	$242.2697	$242.27	$242.25	$242.30
Purchase #6	$67.28	13.169%	$76.1401	$76.14	$76.15	$76.10
Purchase #7	$78.67	5.797%	$83.2305	$83.23	$83.25	$83.20
7 purchase totals =	$805.64		$869.9939	$870.00	$869.95	$869.90