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	$103.42	12.517%	$116.3651	$116.37	$116.35	$116.40
Purchase #2	$132.57	5.351%	$139.6638	$139.66	$139.65	$139.70
Purchase #3	$36.66	4.706%	$38.3852	$38.39	$38.40	$38.40
Purchase #4	$50.39	6.362%	$53.5958	$53.60	$53.60	$53.60
Purchase #5	$66.94	5.499%	$70.621	$70.62	$70.60	$70.60
Purchase #6	$21.92	6.415%	$23.3262	$23.33	$23.35	$23.30
Purchase #7	$64.41	12.566%	$72.5038	$72.50	$72.50	$72.50
7 purchase totals =	$476.31		$514.4609	$514.47	$514.45	$514.50