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	$108.65	8.752%	$118.159	$118.16	$118.15	$118.20
Purchase #2	$109.49	8.242%	$118.5142	$118.51	$118.50	$118.50
Purchase #3	$92.78	13.499%	$105.3044	$105.30	$105.30	$105.30
Purchase #4	$196.47	8.577%	$213.3212	$213.32	$213.30	$213.30
Purchase #5	$118.93	12.149%	$133.3788	$133.38	$133.40	$133.40
Purchase #6	$146.52	12.863%	$165.3669	$165.37	$165.35	$165.40
Purchase #7	$141.71	7.376%	$152.1625	$152.16	$152.15	$152.20
7 purchase totals =	$914.55		$1,006.2070	$1,006.20	$1,006.15	$1,006.30