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	$103.38	7.544%	$111.179	$111.18	$111.20	$111.20
Purchase #2	$108.50	8.714%	$117.9547	$117.95	$117.95	$118.00
Purchase #3	$24.42	5.281%	$25.7096	$25.71	$25.70	$25.70
Purchase #4	$151.41	8.657%	$164.5176	$164.52	$164.50	$164.50
Purchase #5	$90.83	7.758%	$97.8766	$97.88	$97.90	$97.90
Purchase #6	$72.51	12.694%	$81.7144	$81.71	$81.70	$81.70
Purchase #7	$133.81	8.714%	$145.4702	$145.47	$145.45	$145.50
7 purchase totals =	$684.86		$744.4221	$744.42	$744.40	$744.50