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	$209.88	5.398%	$221.2093	$221.21	$221.20	$221.20
Purchase #2	$213.81	9.425%	$233.9616	$233.96	$233.95	$234.00
Purchase #3	$52.73	13.611%	$59.9071	$59.91	$59.90	$59.90
Purchase #4	$57.84	4.388%	$60.378	$60.38	$60.40	$60.40
Purchase #5	$95.97	3.774%	$99.5919	$99.59	$99.60	$99.60
Purchase #6	$131.32	11.831%	$146.8565	$146.86	$146.85	$146.90
Purchase #7	$102.72	8.730%	$111.6875	$111.69	$111.70	$111.70
7 purchase totals =	$864.27		$933.5919	$933.60	$933.60	$933.70