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	$56.35	8.679%	$61.2406	$61.24	$61.25	$61.20
Purchase #2	$78.84	13.454%	$89.4471	$89.45	$89.45	$89.40
Purchase #3	$206.84	4.376%	$215.8913	$215.89	$215.90	$215.90
Purchase #4	$17.92	8.361%	$19.4183	$19.42	$19.40	$19.40
Purchase #5	$37.55	7.366%	$40.3159	$40.32	$40.30	$40.30
Purchase #6	$64.63	8.538%	$70.1481	$70.15	$70.15	$70.10
Purchase #7	$121.32	4.176%	$126.3863	$126.39	$126.40	$126.40
7 purchase totals =	$583.45		$622.8476	$622.86	$622.85	$622.70