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	$15.45	5.563%	$16.3095	$16.31	$16.30	$16.30
Purchase #2	$55.29	4.172%	$57.5967	$57.60	$57.60	$57.60
Purchase #3	$99.46	5.860%	$105.2884	$105.29	$105.30	$105.30
Purchase #4	$230.36	5.768%	$243.6472	$243.65	$243.65	$243.60
Purchase #5	$153.87	12.677%	$173.3761	$173.38	$173.40	$173.40
Purchase #6	$179.42	13.857%	$204.2822	$204.28	$204.30	$204.30
Purchase #7	$127.92	3.155%	$131.9559	$131.96	$131.95	$132.00
7 purchase totals =	$861.77		$932.4560	$932.47	$932.50	$932.50