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	$114.71	3.861%	$119.139	$119.14	$119.15	$119.10
Purchase #2	$128.89	10.588%	$142.5369	$142.54	$142.55	$142.50
Purchase #3	$105.35	10.252%	$116.1505	$116.15	$116.15	$116.20
Purchase #4	$214.94	11.406%	$239.4561	$239.46	$239.45	$239.50
Purchase #5	$240.57	5.727%	$254.3474	$254.35	$254.35	$254.30
Purchase #6	$235.80	11.378%	$262.6293	$262.63	$262.65	$262.60
Purchase #7	$72.27	13.336%	$81.9079	$81.91	$81.90	$81.90
7 purchase totals =	$1,112.53		$1,216.1671	$1,216.18	$1,216.20	$1,216.10