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	$56.38	7.255%	$60.4704	$60.47	$60.45	$60.50
Purchase #2	$224.61	5.474%	$236.9052	$236.91	$236.90	$236.90
Purchase #3	$210.49	10.861%	$233.3513	$233.35	$233.35	$233.40
Purchase #4	$115.52	11.457%	$128.7551	$128.76	$128.75	$128.80
Purchase #5	$118.25	11.871%	$132.2875	$132.29	$132.30	$132.30
Purchase #6	$132.48	12.343%	$148.832	$148.83	$148.85	$148.80
Purchase #7	$104.56	6.549%	$111.4076	$111.41	$111.40	$111.40
7 purchase totals =	$962.29		$1,052.0091	$1,052.02	$1,052.00	$1,052.10