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	$237.31	7.757%	$255.7181	$255.72	$255.70	$255.70
Purchase #2	$42.40	9.136%	$46.2737	$46.27	$46.25	$46.30
Purchase #3	$214.79	12.260%	$241.1233	$241.12	$241.10	$241.10
Purchase #4	$198.38	10.698%	$219.6027	$219.60	$219.60	$219.60
Purchase #5	$180.31	6.635%	$192.2736	$192.27	$192.25	$192.30
Purchase #6	$5.60	5.350%	$5.8996	$5.90	$5.90	$5.90
Purchase #7	$127.93	12.330%	$143.7038	$143.70	$143.70	$143.70
7 purchase totals =	$1,006.72		$1,104.5948	$1,104.58	$1,104.50	$1,104.60