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	$172.81	6.702%	$184.3917	$184.39	$184.40	$184.40
Purchase #2	$170.91	8.322%	$185.1331	$185.13	$185.15	$185.10
Purchase #3	$143.30	3.602%	$148.4617	$148.46	$148.45	$148.50
Purchase #4	$139.66	13.606%	$158.6621	$158.66	$158.65	$158.70
Purchase #5	$25.49	11.361%	$28.3859	$28.39	$28.40	$28.40
Purchase #6	$138.25	5.274%	$145.5413	$145.54	$145.55	$145.50
Purchase #7	$108.86	4.631%	$113.9013	$113.90	$113.90	$113.90
7 purchase totals =	$899.28		$964.4771	$964.47	$964.50	$964.50