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	$175.37	5.781%	$185.5081	$185.51	$185.50	$185.50
Purchase #2	$140.33	13.162%	$158.8002	$158.80	$158.80	$158.80
Purchase #3	$65.45	9.737%	$71.8229	$71.82	$71.80	$71.80
Purchase #4	$119.71	4.376%	$124.9485	$124.95	$124.95	$124.90
Purchase #5	$51.53	5.558%	$54.394	$54.39	$54.40	$54.40
Purchase #6	$144.65	12.872%	$163.2693	$163.27	$163.25	$163.30
Purchase #7	$110.73	3.765%	$114.899	$114.90	$114.90	$114.90
7 purchase totals =	$807.77		$873.6420	$873.64	$873.60	$873.60