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	$228.41	10.866%	$253.229	$253.23	$253.25	$253.20
Purchase #2	$157.86	9.324%	$172.5789	$172.58	$172.60	$172.60
Purchase #3	$71.84	9.357%	$78.5621	$78.56	$78.55	$78.60
Purchase #4	$70.54	12.556%	$79.397	$79.40	$79.40	$79.40
Purchase #5	$126.71	4.452%	$132.3511	$132.35	$132.35	$132.40
Purchase #6	$204.58	9.765%	$224.5572	$224.56	$224.55	$224.60
Purchase #7	$50.64	7.381%	$54.3777	$54.38	$54.40	$54.40
7 purchase totals =	$910.58		$995.0530	$995.06	$995.10	$995.20