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	$57.38	13.692%	$65.2365	$65.24	$65.25	$65.20
Purchase #2	$154.61	6.759%	$165.0601	$165.06	$165.05	$165.10
Purchase #3	$185.48	10.698%	$205.3227	$205.32	$205.30	$205.30
Purchase #4	$188.48	13.451%	$213.8324	$213.83	$213.85	$213.80
Purchase #5	$196.69	11.307%	$218.9297	$218.93	$218.95	$218.90
Purchase #6	$105.31	10.514%	$116.3823	$116.38	$116.40	$116.40
Purchase #7	$59.95	4.174%	$62.4523	$62.45	$62.45	$62.50
7 purchase totals =	$947.90		$1,047.2160	$1,047.21	$1,047.25	$1,047.20