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	$181.30	12.550%	$204.0532	$204.05	$204.05	$204.10
Purchase #2	$207.72	3.528%	$215.0484	$215.05	$215.05	$215.00
Purchase #3	$90.81	10.643%	$100.4749	$100.47	$100.45	$100.50
Purchase #4	$118.57	11.648%	$132.381	$132.38	$132.40	$132.40
Purchase #5	$159.68	3.387%	$165.0884	$165.09	$165.10	$165.10
Purchase #6	$66.93	4.393%	$69.8702	$69.87	$69.85	$69.90
Purchase #7	$95.91	4.795%	$100.5089	$100.51	$100.50	$100.50
7 purchase totals =	$920.92		$987.4250	$987.42	$987.40	$987.50