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	$221.88	5.721%	$234.5738	$234.57	$234.55	$234.60
Purchase #2	$76.49	12.246%	$85.857	$85.86	$85.85	$85.90
Purchase #3	$79.87	7.423%	$85.7988	$85.80	$85.80	$85.80
Purchase #4	$84.45	7.671%	$90.9282	$90.93	$90.95	$90.90
Purchase #5	$70.85	12.308%	$79.5702	$79.57	$79.55	$79.60
Purchase #6	$109.62	13.315%	$124.2159	$124.22	$124.20	$124.20
Purchase #7	$126.32	13.866%	$143.8355	$143.84	$143.85	$143.80
7 purchase totals =	$769.48		$844.7794	$844.79	$844.75	$844.80