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	$143.72	3.233%	$148.3665	$148.37	$148.35	$148.40
Purchase #2	$150.47	11.383%	$167.598	$167.60	$167.60	$167.60
Purchase #3	$173.43	7.749%	$186.8691	$186.87	$186.85	$186.90
Purchase #4	$235.31	6.493%	$250.5887	$250.59	$250.60	$250.60
Purchase #5	$137.97	12.143%	$154.7237	$154.72	$154.70	$154.70
Purchase #6	$207.83	5.377%	$219.005	$219.01	$219.00	$219.00
Purchase #7	$206.28	13.333%	$233.7833	$233.78	$233.80	$233.80
7 purchase totals =	$1,255.01		$1,360.9343	$1,360.94	$1,360.90	$1,361.00