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	$100.77	4.801%	$105.608	$105.61	$105.60	$105.60
Purchase #2	$12.40	8.304%	$13.4297	$13.43	$13.45	$13.40
Purchase #3	$41.70	13.603%	$47.3725	$47.37	$47.35	$47.40
Purchase #4	$82.37	12.390%	$92.5756	$92.58	$92.60	$92.60
Purchase #5	$161.64	10.675%	$178.8951	$178.90	$178.90	$178.90
Purchase #6	$145.89	7.488%	$156.8142	$156.81	$156.80	$156.80
Purchase #7	$55.99	4.803%	$58.6792	$58.68	$58.70	$58.70
7 purchase totals =	$600.76		$653.3743	$653.38	$653.40	$653.40