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	$148.62	5.136%	$156.2531	$156.25	$156.25	$156.30
Purchase #2	$136.77	3.420%	$141.4475	$141.45	$141.45	$141.40
Purchase #3	$168.50	7.642%	$181.3768	$181.38	$181.40	$181.40
Purchase #4	$116.52	10.689%	$128.9748	$128.97	$128.95	$129.00
Purchase #5	$90.58	4.721%	$94.8563	$94.86	$94.85	$94.90
Purchase #6	$171.81	11.714%	$191.9358	$191.94	$191.95	$191.90
Purchase #7	$68.88	5.433%	$72.6223	$72.62	$72.60	$72.60
7 purchase totals =	$901.68		$967.4666	$967.47	$967.45	$967.50