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	$53.82	10.434%	$59.4356	$59.44	$59.45	$59.40
Purchase #2	$189.56	9.562%	$207.6857	$207.69	$207.70	$207.70
Purchase #3	$87.60	5.560%	$92.4706	$92.47	$92.45	$92.50
Purchase #4	$19.36	8.369%	$20.9802	$20.98	$21.00	$21.00
Purchase #5	$18.60	10.161%	$20.4899	$20.49	$20.50	$20.50
Purchase #6	$131.54	8.763%	$143.0669	$143.07	$143.05	$143.10
Purchase #7	$224.37	10.239%	$247.3432	$247.34	$247.35	$247.30
7 purchase totals =	$724.85		$791.4721	$791.48	$791.50	$791.50