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	$173.64	10.848%	$192.4765	$192.48	$192.50	$192.50
Purchase #2	$87.36	7.776%	$94.1531	$94.15	$94.15	$94.20
Purchase #3	$234.41	6.710%	$250.1389	$250.14	$250.15	$250.10
Purchase #4	$53.90	4.170%	$56.1476	$56.15	$56.15	$56.10
Purchase #5	$109.52	4.480%	$114.4265	$114.43	$114.45	$114.40
Purchase #6	$42.64	11.272%	$47.4464	$47.45	$47.45	$47.40
Purchase #7	$203.94	5.164%	$214.4715	$214.47	$214.45	$214.50
7 purchase totals =	$905.41		$969.2605	$969.27	$969.30	$969.20