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	$31.28	12.346%	$35.1418	$35.14	$35.15	$35.10
Purchase #2	$232.99	9.658%	$255.4922	$255.49	$255.50	$255.50
Purchase #3	$195.87	13.395%	$222.1068	$222.11	$222.10	$222.10
Purchase #4	$34.58	7.865%	$37.2997	$37.30	$37.30	$37.30
Purchase #5	$108.77	4.496%	$113.6603	$113.66	$113.65	$113.70
Purchase #6	$79.56	4.319%	$82.9962	$83.00	$83.00	$83.00
Purchase #7	$74.59	10.512%	$82.4309	$82.43	$82.45	$82.40
7 purchase totals =	$757.64		$829.1279	$829.13	$829.15	$829.10