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	$42.66	8.751%	$46.3932	$46.39	$46.40	$46.40
Purchase #2	$74.34	9.707%	$81.5562	$81.56	$81.55	$81.60
Purchase #3	$56.87	5.291%	$59.879	$59.88	$59.90	$59.90
Purchase #4	$179.85	13.873%	$204.8006	$204.80	$204.80	$204.80
Purchase #5	$11.88	10.772%	$13.1597	$13.16	$13.15	$13.20
Purchase #6	$87.46	13.523%	$99.2872	$99.29	$99.30	$99.30
Purchase #7	$46.78	4.832%	$49.0404	$49.04	$49.05	$49.00
7 purchase totals =	$499.84		$554.1163	$554.12	$554.15	$554.20