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	$154.44	5.400%	$162.7798	$162.78	$162.80	$162.80
Purchase #2	$33.87	6.303%	$36.0048	$36.00	$36.00	$36.00
Purchase #3	$97.33	8.307%	$105.4152	$105.42	$105.40	$105.40
Purchase #4	$192.32	6.379%	$204.5881	$204.59	$204.60	$204.60
Purchase #5	$205.25	8.412%	$222.5156	$222.52	$222.50	$222.50
Purchase #6	$145.67	13.708%	$165.6384	$165.64	$165.65	$165.60
Purchase #7	$138.65	3.857%	$143.9977	$144.00	$144.00	$144.00
7 purchase totals =	$967.53		$1,040.9396	$1,040.95	$1,040.95	$1,040.90