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	$175.40	12.193%	$196.7865	$196.79	$196.80	$196.80
Purchase #2	$98.83	6.219%	$104.9762	$104.98	$105.00	$105.00
Purchase #3	$153.97	13.674%	$175.0239	$175.02	$175.00	$175.00
Purchase #4	$164.52	5.747%	$173.975	$173.98	$174.00	$174.00
Purchase #5	$232.40	7.477%	$249.7765	$249.78	$249.80	$249.80
Purchase #6	$20.79	9.803%	$22.828	$22.83	$22.85	$22.80
Purchase #7	$65.86	10.233%	$72.5995	$72.60	$72.60	$72.60
7 purchase totals =	$911.77		$995.9656	$995.98	$996.05	$996.00