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	$29.37	13.798%	$33.4225	$33.42	$33.40	$33.40
Purchase #2	$230.93	5.652%	$243.9822	$243.98	$244.00	$244.00
Purchase #3	$49.89	3.267%	$51.5199	$51.52	$51.50	$51.50
Purchase #4	$29.92	13.309%	$33.9021	$33.90	$33.90	$33.90
Purchase #5	$144.47	6.784%	$154.2708	$154.27	$154.25	$154.30
Purchase #6	$240.44	7.736%	$259.0404	$259.04	$259.05	$259.00
Purchase #7	$108.99	13.253%	$123.4344	$123.43	$123.45	$123.40
7 purchase totals =	$834.01		$899.5723	$899.56	$899.55	$899.50