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	$107.37	8.457%	$116.4503	$116.45	$116.45	$116.50
Purchase #2	$77.39	10.672%	$85.6491	$85.65	$85.65	$85.60
Purchase #3	$74.69	10.307%	$82.3883	$82.39	$82.40	$82.40
Purchase #4	$162.95	6.581%	$173.6737	$173.67	$173.65	$173.70
Purchase #5	$45.62	11.708%	$50.9612	$50.96	$50.95	$51.00
Purchase #6	$25.90	6.683%	$27.6309	$27.63	$27.65	$27.60
Purchase #7	$137.79	7.609%	$148.2744	$148.27	$148.25	$148.30
7 purchase totals =	$631.71		$685.0279	$685.02	$685.00	$685.10