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	$63.56	11.109%	$70.6209	$70.62	$70.60	$70.60
Purchase #2	$36.45	6.705%	$38.894	$38.89	$38.90	$38.90
Purchase #3	$140.48	4.352%	$146.5937	$146.59	$146.60	$146.60
Purchase #4	$222.35	9.325%	$243.0841	$243.08	$243.10	$243.10
Purchase #5	$217.37	3.824%	$225.6822	$225.68	$225.70	$225.70
Purchase #6	$66.65	6.102%	$70.717	$70.72	$70.70	$70.70
Purchase #7	$200.37	11.822%	$224.0577	$224.06	$224.05	$224.10
7 purchase totals =	$947.23		$1,019.6496	$1,019.64	$1,019.65	$1,019.70