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	$155.35	5.550%	$163.9719	$163.97	$163.95	$164.00
Purchase #2	$132.85	8.697%	$144.404	$144.40	$144.40	$144.40
Purchase #3	$231.92	13.613%	$263.4913	$263.49	$263.50	$263.50
Purchase #4	$223.79	6.109%	$237.4613	$237.46	$237.45	$237.50
Purchase #5	$73.72	6.512%	$78.5206	$78.52	$78.50	$78.50
Purchase #6	$131.94	12.547%	$148.4945	$148.49	$148.50	$148.50
Purchase #7	$106.77	12.189%	$119.7842	$119.78	$119.80	$119.80
7 purchase totals =	$1,056.34		$1,156.1278	$1,156.11	$1,156.10	$1,156.20