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	$241.47	5.658%	$255.1324	$255.13	$255.15	$255.10
Purchase #2	$174.31	3.552%	$180.5015	$180.50	$180.50	$180.50
Purchase #3	$101.31	4.763%	$106.1354	$106.14	$106.15	$106.10
Purchase #4	$148.37	5.216%	$156.109	$156.11	$156.10	$156.10
Purchase #5	$222.53	6.773%	$237.602	$237.60	$237.60	$237.60
Purchase #6	$32.35	8.608%	$35.1347	$35.13	$35.15	$35.10
Purchase #7	$182.80	12.635%	$205.8968	$205.90	$205.90	$205.90
7 purchase totals =	$1,103.14		$1,176.5118	$1,176.51	$1,176.55	$1,176.40