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	$119.59	6.432%	$127.282	$127.28	$127.30	$127.30
Purchase #2	$133.67	5.468%	$140.9791	$140.98	$141.00	$141.00
Purchase #3	$208.77	8.866%	$227.2795	$227.28	$227.30	$227.30
Purchase #4	$190.45	9.297%	$208.1561	$208.16	$208.15	$208.20
Purchase #5	$232.79	7.531%	$250.3214	$250.32	$250.30	$250.30
Purchase #6	$57.71	10.413%	$63.7193	$63.72	$63.70	$63.70
Purchase #7	$76.47	6.665%	$81.5667	$81.57	$81.55	$81.60
7 purchase totals =	$1,019.45		$1,099.3041	$1,099.31	$1,099.30	$1,099.40