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	$149.48	11.337%	$166.4265	$166.43	$166.45	$166.40
Purchase #2	$104.73	7.441%	$112.523	$112.52	$112.50	$112.50
Purchase #3	$206.96	5.631%	$218.6139	$218.61	$218.60	$218.60
Purchase #4	$209.94	4.174%	$218.7029	$218.70	$218.70	$218.70
Purchase #5	$58.77	13.654%	$66.7945	$66.79	$66.80	$66.80
Purchase #6	$161.59	12.382%	$181.5981	$181.60	$181.60	$181.60
Purchase #7	$224.74	3.189%	$231.907	$231.91	$231.90	$231.90
7 purchase totals =	$1,116.21		$1,196.5659	$1,196.56	$1,196.55	$1,196.50