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	$178.51	11.338%	$198.7495	$198.75	$198.75	$198.70
Purchase #2	$86.77	4.238%	$90.4473	$90.45	$90.45	$90.40
Purchase #3	$90.83	5.187%	$95.5414	$95.54	$95.55	$95.50
Purchase #4	$103.87	11.712%	$116.0353	$116.04	$116.05	$116.00
Purchase #5	$64.58	11.709%	$72.1417	$72.14	$72.15	$72.10
Purchase #6	$203.51	5.412%	$214.524	$214.52	$214.50	$214.50
Purchase #7	$179.34	5.303%	$188.8504	$188.85	$188.85	$188.90
7 purchase totals =	$907.41		$976.2896	$976.29	$976.30	$976.10