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	$146.82	5.427%	$154.7879	$154.79	$154.80	$154.80
Purchase #2	$45.42	11.128%	$50.4743	$50.47	$50.45	$50.50
Purchase #3	$177.36	7.489%	$190.6425	$190.64	$190.65	$190.60
Purchase #4	$112.60	5.192%	$118.4462	$118.45	$118.45	$118.40
Purchase #5	$168.55	10.480%	$186.214	$186.21	$186.20	$186.20
Purchase #6	$102.69	13.788%	$116.8489	$116.85	$116.85	$116.80
Purchase #7	$192.27	3.685%	$199.3551	$199.36	$199.35	$199.40
7 purchase totals =	$945.71		$1,016.7689	$1,016.77	$1,016.75	$1,016.70