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	$111.44	4.222%	$116.145	$116.15	$116.15	$116.10
Purchase #2	$46.54	5.766%	$49.2235	$49.22	$49.20	$49.20
Purchase #3	$149.45	10.173%	$164.6535	$164.65	$164.65	$164.70
Purchase #4	$87.71	12.153%	$98.3694	$98.37	$98.35	$98.40
Purchase #5	$112.69	9.684%	$123.6029	$123.60	$123.60	$123.60
Purchase #6	$161.84	4.161%	$168.5742	$168.57	$168.55	$168.60
Purchase #7	$97.47	7.181%	$104.4693	$104.47	$104.45	$104.50
7 purchase totals =	$767.14		$825.0378	$825.03	$824.95	$825.10