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	$37.76	10.300%	$41.6493	$41.65	$41.65	$41.60
Purchase #2	$48.92	7.667%	$52.6707	$52.67	$52.65	$52.70
Purchase #3	$52.89	4.277%	$55.1521	$55.15	$55.15	$55.20
Purchase #4	$156.77	10.505%	$173.2387	$173.24	$173.25	$173.20
Purchase #5	$134.86	7.348%	$144.7695	$144.77	$144.75	$144.80
Purchase #6	$147.95	3.514%	$153.149	$153.15	$153.15	$153.10
Purchase #7	$100.72	5.123%	$105.8799	$105.88	$105.90	$105.90
7 purchase totals =	$679.87		$726.5092	$726.51	$726.50	$726.50