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	$32.52	13.622%	$36.9499	$36.95	$36.95	$36.90
Purchase #2	$62.43	4.783%	$65.416	$65.42	$65.40	$65.40
Purchase #3	$103.60	10.275%	$114.2449	$114.24	$114.25	$114.20
Purchase #4	$100.93	4.363%	$105.3336	$105.33	$105.35	$105.30
Purchase #5	$41.77	4.762%	$43.7591	$43.76	$43.75	$43.80
Purchase #6	$38.26	10.384%	$42.2329	$42.23	$42.25	$42.20
Purchase #7	$168.81	6.483%	$179.754	$179.75	$179.75	$179.80
7 purchase totals =	$548.32		$587.6904	$587.68	$587.70	$587.60