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	$83.83	10.129%	$92.3211	$92.32	$92.30	$92.30
Purchase #2	$156.89	5.444%	$165.4311	$165.43	$165.45	$165.40
Purchase #3	$50.67	11.499%	$56.4965	$56.50	$56.50	$56.50
Purchase #4	$82.55	3.366%	$85.3286	$85.33	$85.35	$85.30
Purchase #5	$201.67	12.262%	$226.3988	$226.40	$226.40	$226.40
Purchase #6	$235.60	8.339%	$255.2467	$255.25	$255.25	$255.20
Purchase #7	$131.99	12.846%	$148.9454	$148.95	$148.95	$148.90
7 purchase totals =	$943.20		$1,030.1682	$1,030.18	$1,030.20	$1,030.00