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	$123.96	8.673%	$134.7111	$134.71	$134.70	$134.70
Purchase #2	$136.56	3.376%	$141.1703	$141.17	$141.15	$141.20
Purchase #3	$185.92	13.808%	$211.5918	$211.59	$211.60	$211.60
Purchase #4	$20.28	11.387%	$22.5893	$22.59	$22.60	$22.60
Purchase #5	$89.67	6.862%	$95.8232	$95.82	$95.80	$95.80
Purchase #6	$47.95	3.649%	$49.6997	$49.70	$49.70	$49.70
Purchase #7	$90.66	9.525%	$99.2954	$99.30	$99.30	$99.30
7 purchase totals =	$695.00		$754.8808	$754.88	$754.85	$754.90