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	$116.27	12.584%	$130.9014	$130.90	$130.90	$130.90
Purchase #2	$130.47	8.296%	$141.2938	$141.29	$141.30	$141.30
Purchase #3	$158.50	8.704%	$172.2958	$172.30	$172.30	$172.30
Purchase #4	$23.37	5.185%	$24.5817	$24.58	$24.60	$24.60
Purchase #5	$22.67	12.830%	$25.5786	$25.58	$25.60	$25.60
Purchase #6	$222.34	8.575%	$241.4057	$241.41	$241.40	$241.40
Purchase #7	$83.77	8.286%	$90.7112	$90.71	$90.70	$90.70
7 purchase totals =	$757.39		$826.7682	$826.77	$826.80	$826.80