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	$54.45	9.619%	$59.6875	$59.69	$59.70	$59.70
Purchase #2	$41.42	6.547%	$44.1318	$44.13	$44.15	$44.10
Purchase #3	$87.76	9.173%	$95.8102	$95.81	$95.80	$95.80
Purchase #4	$87.41	9.278%	$95.5199	$95.52	$95.50	$95.50
Purchase #5	$127.30	11.137%	$141.4774	$141.48	$141.50	$141.50
Purchase #6	$247.91	4.552%	$259.1949	$259.19	$259.20	$259.20
Purchase #7	$11.54	13.719%	$13.1232	$13.12	$13.10	$13.10
7 purchase totals =	$657.79		$708.9449	$708.94	$708.95	$708.90