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	$172.57	13.778%	$196.3467	$196.35	$196.35	$196.30
Purchase #2	$119.85	9.738%	$131.521	$131.52	$131.50	$131.50
Purchase #3	$24.29	13.501%	$27.5694	$27.57	$27.55	$27.60
Purchase #4	$63.56	4.831%	$66.6306	$66.63	$66.65	$66.60
Purchase #5	$231.52	9.229%	$252.887	$252.89	$252.90	$252.90
Purchase #6	$141.85	9.715%	$155.6307	$155.63	$155.65	$155.60
Purchase #7	$98.38	13.710%	$111.8679	$111.87	$111.85	$111.90
7 purchase totals =	$852.02		$942.4533	$942.46	$942.45	$942.40