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	$178.90	10.692%	$198.028	$198.03	$198.05	$198.00
Purchase #2	$175.49	13.171%	$198.6038	$198.60	$198.60	$198.60
Purchase #3	$101.33	7.431%	$108.8598	$108.86	$108.85	$108.90
Purchase #4	$127.83	6.606%	$136.2744	$136.27	$136.25	$136.30
Purchase #5	$168.71	9.111%	$184.0812	$184.08	$184.10	$184.10
Purchase #6	$111.76	4.182%	$116.4338	$116.43	$116.45	$116.40
Purchase #7	$242.46	12.175%	$271.9795	$271.98	$272.00	$272.00
7 purchase totals =	$1,106.48		$1,214.2605	$1,214.25	$1,214.30	$1,214.30