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	$59.40	4.186%	$61.8865	$61.89	$61.90	$61.90
Purchase #2	$207.32	10.756%	$229.6193	$229.62	$229.60	$229.60
Purchase #3	$102.99	4.152%	$107.2661	$107.27	$107.25	$107.30
Purchase #4	$29.77	10.361%	$32.8545	$32.85	$32.85	$32.90
Purchase #5	$233.89	4.105%	$243.4912	$243.49	$243.50	$243.50
Purchase #6	$204.76	9.126%	$223.4464	$223.45	$223.45	$223.40
Purchase #7	$48.84	10.546%	$53.9907	$53.99	$54.00	$54.00
7 purchase totals =	$886.97		$952.5547	$952.56	$952.55	$952.60