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	$80.29	8.701%	$87.276	$87.28	$87.30	$87.30
Purchase #2	$136.90	3.170%	$141.2397	$141.24	$141.25	$141.20
Purchase #3	$175.45	11.683%	$195.9478	$195.95	$195.95	$195.90
Purchase #4	$92.53	5.391%	$97.5183	$97.52	$97.50	$97.50
Purchase #5	$137.96	13.303%	$156.3128	$156.31	$156.30	$156.30
Purchase #6	$48.29	10.552%	$53.3856	$53.39	$53.40	$53.40
Purchase #7	$48.79	12.520%	$54.8985	$54.90	$54.90	$54.90
7 purchase totals =	$720.21		$786.5787	$786.59	$786.60	$786.50