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	$33.82	13.787%	$38.4828	$38.48	$38.50	$38.50
Purchase #2	$62.48	4.236%	$65.1267	$65.13	$65.15	$65.10
Purchase #3	$142.72	3.697%	$147.9964	$148.00	$148.00	$148.00
Purchase #4	$128.76	8.615%	$139.8527	$139.85	$139.85	$139.90
Purchase #5	$106.25	9.530%	$116.3756	$116.38	$116.40	$116.40
Purchase #6	$233.45	4.241%	$243.3506	$243.35	$243.35	$243.40
Purchase #7	$235.60	11.340%	$262.317	$262.32	$262.30	$262.30
7 purchase totals =	$943.08		$1,013.5018	$1,013.51	$1,013.55	$1,013.60