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	$167.60	13.530%	$190.2763	$190.28	$190.30	$190.30
Purchase #2	$15.96	12.177%	$17.9034	$17.90	$17.90	$17.90
Purchase #3	$219.43	11.728%	$245.1648	$245.16	$245.15	$245.20
Purchase #4	$55.58	11.780%	$62.1273	$62.13	$62.15	$62.10
Purchase #5	$103.86	7.742%	$111.9008	$111.90	$111.90	$111.90
Purchase #6	$109.44	13.255%	$123.9463	$123.95	$123.95	$123.90
Purchase #7	$200.63	11.456%	$223.6142	$223.61	$223.60	$223.60
7 purchase totals =	$872.50		$974.9331	$974.93	$974.95	$974.90