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	$234.97	11.271%	$261.4535	$261.45	$261.45	$261.50
Purchase #2	$94.62	7.678%	$101.8849	$101.88	$101.90	$101.90
Purchase #3	$161.97	6.747%	$172.8981	$172.90	$172.90	$172.90
Purchase #4	$223.55	7.814%	$241.0182	$241.02	$241.00	$241.00
Purchase #5	$169.35	9.323%	$185.1385	$185.14	$185.15	$185.10
Purchase #6	$118.36	5.566%	$124.9479	$124.95	$124.95	$124.90
Purchase #7	$92.52	8.242%	$100.1455	$100.15	$100.15	$100.10
7 purchase totals =	$1,095.34		$1,187.4866	$1,187.49	$1,187.50	$1,187.40