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	$42.85	3.350%	$44.2855	$44.29	$44.30	$44.30
Purchase #2	$173.38	9.591%	$190.0089	$190.01	$190.00	$190.00
Purchase #3	$158.33	7.574%	$170.3219	$170.32	$170.30	$170.30
Purchase #4	$169.84	5.227%	$178.7175	$178.72	$178.70	$178.70
Purchase #5	$156.46	7.203%	$167.7298	$167.73	$167.75	$167.70
Purchase #6	$162.91	6.748%	$173.9032	$173.90	$173.90	$173.90
Purchase #7	$100.70	10.239%	$111.0107	$111.01	$111.00	$111.00
7 purchase totals =	$964.47		$1,035.9775	$1,035.98	$1,035.95	$1,035.90