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	$220.87	13.368%	$250.3959	$250.40	$250.40	$250.40
Purchase #2	$9.81	4.613%	$10.2625	$10.26	$10.25	$10.30
Purchase #3	$242.49	5.244%	$255.2062	$255.21	$255.20	$255.20
Purchase #4	$59.82	10.836%	$66.3021	$66.30	$66.30	$66.30
Purchase #5	$52.36	9.591%	$57.3818	$57.38	$57.40	$57.40
Purchase #6	$203.34	13.834%	$231.4701	$231.47	$231.45	$231.50
Purchase #7	$121.41	8.440%	$131.657	$131.66	$131.65	$131.70
7 purchase totals =	$910.10		$1,002.6756	$1,002.68	$1,002.65	$1,002.80