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	$205.61	10.433%	$227.0613	$227.06	$227.05	$227.10
Purchase #2	$68.69	9.155%	$74.9786	$74.98	$75.00	$75.00
Purchase #3	$19.72	6.740%	$21.0491	$21.05	$21.05	$21.00
Purchase #4	$217.50	12.439%	$244.5548	$244.55	$244.55	$244.60
Purchase #5	$105.38	5.540%	$111.2181	$111.22	$111.20	$111.20
Purchase #6	$244.61	11.204%	$272.0161	$272.02	$272.00	$272.00
Purchase #7	$21.88	12.504%	$24.6159	$24.62	$24.60	$24.60
7 purchase totals =	$883.39		$975.4939	$975.50	$975.45	$975.50