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	$77.93	9.828%	$85.589	$85.59	$85.60	$85.60
Purchase #2	$152.45	3.643%	$158.0038	$158.00	$158.00	$158.00
Purchase #3	$223.51	3.737%	$231.8626	$231.86	$231.85	$231.90
Purchase #4	$19.93	7.637%	$21.4521	$21.45	$21.45	$21.50
Purchase #5	$208.78	7.355%	$224.1358	$224.14	$224.15	$224.10
Purchase #6	$139.51	3.277%	$144.0817	$144.08	$144.10	$144.10
Purchase #7	$185.69	9.551%	$203.4253	$203.43	$203.45	$203.40
7 purchase totals =	$1,007.80		$1,068.5503	$1,068.55	$1,068.60	$1,068.60