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	$29.61	6.759%	$31.6113	$31.61	$31.60	$31.60
Purchase #2	$54.87	7.608%	$59.0445	$59.04	$59.05	$59.00
Purchase #3	$66.65	11.212%	$74.1228	$74.12	$74.10	$74.10
Purchase #4	$177.30	12.470%	$199.4093	$199.41	$199.40	$199.40
Purchase #5	$219.74	12.761%	$247.781	$247.78	$247.80	$247.80
Purchase #6	$33.32	12.609%	$37.5213	$37.52	$37.50	$37.50
Purchase #7	$153.98	5.576%	$162.5659	$162.57	$162.55	$162.60
7 purchase totals =	$735.47		$812.0561	$812.05	$812.00	$812.00