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	$61.55	8.757%	$66.9399	$66.94	$66.95	$66.90
Purchase #2	$18.31	11.544%	$20.4237	$20.42	$20.40	$20.40
Purchase #3	$150.48	4.631%	$157.4487	$157.45	$157.45	$157.40
Purchase #4	$9.51	5.159%	$10.0006	$10.00	$10.00	$10.00
Purchase #5	$178.80	4.738%	$187.2715	$187.27	$187.25	$187.30
Purchase #6	$35.84	5.553%	$37.8302	$37.83	$37.85	$37.80
Purchase #7	$66.77	8.485%	$72.4354	$72.44	$72.45	$72.40
7 purchase totals =	$521.26		$552.3500	$552.35	$552.35	$552.20