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	$169.42	12.606%	$190.7771	$190.78	$190.80	$190.80
Purchase #2	$80.33	6.103%	$85.2325	$85.23	$85.25	$85.20
Purchase #3	$190.86	3.753%	$198.023	$198.02	$198.00	$198.00
Purchase #4	$137.40	12.476%	$154.542	$154.54	$154.55	$154.50
Purchase #5	$85.94	5.666%	$90.8094	$90.81	$90.80	$90.80
Purchase #6	$131.82	12.546%	$148.3581	$148.36	$148.35	$148.40
Purchase #7	$221.65	4.493%	$231.6087	$231.61	$231.60	$231.60
7 purchase totals =	$1,017.42		$1,099.3508	$1,099.35	$1,099.35	$1,099.30