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	$118.96	11.359%	$132.4727	$132.47	$132.45	$132.50
Purchase #2	$181.49	13.118%	$205.2979	$205.30	$205.30	$205.30
Purchase #3	$64.60	11.712%	$72.166	$72.17	$72.15	$72.20
Purchase #4	$78.32	5.466%	$82.601	$82.60	$82.60	$82.60
Purchase #5	$58.45	4.797%	$61.2538	$61.25	$61.25	$61.30
Purchase #6	$139.68	12.368%	$156.9556	$156.96	$156.95	$157.00
Purchase #7	$70.78	5.721%	$74.8293	$74.83	$74.85	$74.80
7 purchase totals =	$712.28		$785.5763	$785.58	$785.55	$785.70