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	$85.47	10.322%	$94.2922	$94.29	$94.30	$94.30
Purchase #2	$132.59	13.144%	$150.0176	$150.02	$150.00	$150.00
Purchase #3	$48.77	10.398%	$53.8411	$53.84	$53.85	$53.80
Purchase #4	$61.40	10.340%	$67.7488	$67.75	$67.75	$67.70
Purchase #5	$240.93	9.216%	$263.1341	$263.13	$263.15	$263.10
Purchase #6	$64.42	5.117%	$67.7164	$67.72	$67.70	$67.70
Purchase #7	$205.65	8.265%	$222.647	$222.65	$222.65	$222.60
7 purchase totals =	$839.23		$919.3972	$919.40	$919.40	$919.20