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	$107.84	3.697%	$111.8268	$111.83	$111.85	$111.80
Purchase #2	$66.62	11.639%	$74.3739	$74.37	$74.35	$74.40
Purchase #3	$249.52	3.462%	$258.1584	$258.16	$258.15	$258.20
Purchase #4	$149.62	10.392%	$165.1685	$165.17	$165.15	$165.20
Purchase #5	$99.72	13.571%	$113.253	$113.25	$113.25	$113.30
Purchase #6	$206.67	13.561%	$234.6965	$234.70	$234.70	$234.70
Purchase #7	$189.60	10.172%	$208.8861	$208.89	$208.90	$208.90
7 purchase totals =	$1,069.59		$1,166.3632	$1,166.37	$1,166.35	$1,166.50