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	$163.87	9.108%	$178.7953	$178.80	$178.80	$178.80
Purchase #2	$100.89	13.154%	$114.1611	$114.16	$114.15	$114.20
Purchase #3	$139.49	9.138%	$152.2366	$152.24	$152.25	$152.20
Purchase #4	$108.49	7.520%	$116.6484	$116.65	$116.65	$116.60
Purchase #5	$18.51	13.294%	$20.9707	$20.97	$20.95	$21.00
Purchase #6	$180.88	5.539%	$190.8989	$190.90	$190.90	$190.90
Purchase #7	$221.46	8.798%	$240.9441	$240.94	$240.95	$240.90
7 purchase totals =	$933.59		$1,014.6551	$1,014.66	$1,014.65	$1,014.60