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	$237.28	12.329%	$266.5343	$266.53	$266.55	$266.50
Purchase #2	$158.83	12.705%	$179.0094	$179.01	$179.00	$179.00
Purchase #3	$201.79	7.708%	$217.344	$217.34	$217.35	$217.30
Purchase #4	$100.87	10.806%	$111.77	$111.77	$111.75	$111.80
Purchase #5	$41.28	4.308%	$43.0583	$43.06	$43.05	$43.10
Purchase #6	$32.58	11.771%	$36.415	$36.42	$36.40	$36.40
Purchase #7	$149.33	6.376%	$158.8513	$158.85	$158.85	$158.90
7 purchase totals =	$921.96		$1,012.9823	$1,012.98	$1,012.95	$1,013.00