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	$167.42	3.182%	$172.7473	$172.75	$172.75	$172.70
Purchase #2	$95.92	7.711%	$103.3164	$103.32	$103.30	$103.30
Purchase #3	$134.36	3.491%	$139.0505	$139.05	$139.05	$139.10
Purchase #4	$178.28	10.270%	$196.5894	$196.59	$196.60	$196.60
Purchase #5	$132.89	7.786%	$143.2368	$143.24	$143.25	$143.20
Purchase #6	$136.65	3.440%	$141.3508	$141.35	$141.35	$141.40
Purchase #7	$50.59	3.783%	$52.5038	$52.50	$52.50	$52.50
7 purchase totals =	$896.11		$948.7950	$948.80	$948.80	$948.80