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	$104.93	11.385%	$116.8763	$116.88	$116.90	$116.90
Purchase #2	$19.55	8.446%	$21.2012	$21.20	$21.20	$21.20
Purchase #3	$144.25	12.765%	$162.6635	$162.66	$162.65	$162.70
Purchase #4	$138.65	5.390%	$146.1232	$146.12	$146.10	$146.10
Purchase #5	$156.90	9.286%	$171.4697	$171.47	$171.45	$171.50
Purchase #6	$180.49	8.618%	$196.0446	$196.04	$196.05	$196.00
Purchase #7	$222.90	8.247%	$241.2826	$241.28	$241.30	$241.30
7 purchase totals =	$967.67		$1,055.6611	$1,055.65	$1,055.65	$1,055.70