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	$218.75	5.292%	$230.3263	$230.33	$230.35	$230.30
Purchase #2	$62.70	4.145%	$65.2989	$65.30	$65.30	$65.30
Purchase #3	$166.79	8.185%	$180.4418	$180.44	$180.45	$180.40
Purchase #4	$45.49	10.744%	$50.3774	$50.38	$50.40	$50.40
Purchase #5	$70.78	10.605%	$78.2862	$78.29	$78.30	$78.30
Purchase #6	$226.63	10.192%	$249.7281	$249.73	$249.75	$249.70
Purchase #7	$225.50	3.348%	$233.0497	$233.05	$233.05	$233.00
7 purchase totals =	$1,016.64		$1,087.5084	$1,087.52	$1,087.60	$1,087.40