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	$71.29	8.719%	$77.5058	$77.51	$77.50	$77.50
Purchase #2	$32.92	11.205%	$36.6087	$36.61	$36.60	$36.60
Purchase #3	$50.63	5.758%	$53.5453	$53.55	$53.55	$53.50
Purchase #4	$177.38	12.480%	$199.517	$199.52	$199.50	$199.50
Purchase #5	$184.80	7.349%	$198.381	$198.38	$198.40	$198.40
Purchase #6	$54.77	12.199%	$61.4514	$61.45	$61.45	$61.50
Purchase #7	$87.99	8.466%	$95.4392	$95.44	$95.45	$95.40
7 purchase totals =	$659.78		$722.4484	$722.46	$722.45	$722.40