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	$62.82	4.522%	$65.6607	$65.66	$65.65	$65.70
Purchase #2	$57.75	3.572%	$59.8128	$59.81	$59.80	$59.80
Purchase #3	$65.82	10.161%	$72.508	$72.51	$72.50	$72.50
Purchase #4	$241.27	12.170%	$270.6326	$270.63	$270.65	$270.60
Purchase #5	$11.80	5.549%	$12.4548	$12.45	$12.45	$12.50
Purchase #6	$48.65	10.262%	$53.6425	$53.64	$53.65	$53.60
Purchase #7	$66.94	3.371%	$69.1965	$69.20	$69.20	$69.20
7 purchase totals =	$555.05		$603.9079	$603.90	$603.90	$603.90