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	$247.42	8.347%	$268.0721	$268.07	$268.05	$268.10
Purchase #2	$60.65	10.256%	$66.8703	$66.87	$66.85	$66.90
Purchase #3	$55.29	10.522%	$61.1076	$61.11	$61.10	$61.10
Purchase #4	$59.25	11.256%	$65.9192	$65.92	$65.90	$65.90
Purchase #5	$34.93	7.209%	$37.4481	$37.45	$37.45	$37.40
Purchase #6	$68.80	5.775%	$72.7732	$72.77	$72.75	$72.80
Purchase #7	$79.52	7.255%	$85.2892	$85.29	$85.30	$85.30
7 purchase totals =	$605.86		$657.4797	$657.48	$657.40	$657.50