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	$96.28	9.697%	$105.6163	$105.62	$105.60	$105.60
Purchase #2	$143.83	12.212%	$161.3945	$161.39	$161.40	$161.40
Purchase #3	$195.64	10.340%	$215.8692	$215.87	$215.85	$215.90
Purchase #4	$19.61	3.181%	$20.2338	$20.23	$20.25	$20.20
Purchase #5	$12.56	9.520%	$13.7557	$13.76	$13.75	$13.80
Purchase #6	$53.83	13.584%	$61.1423	$61.14	$61.15	$61.10
Purchase #7	$52.79	7.435%	$56.7149	$56.71	$56.70	$56.70
7 purchase totals =	$574.54		$634.7267	$634.72	$634.70	$634.70