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	$111.52	9.715%	$122.3542	$122.35	$122.35	$122.40
Purchase #2	$134.57	5.260%	$141.6484	$141.65	$141.65	$141.60
Purchase #3	$67.82	5.364%	$71.4579	$71.46	$71.45	$71.50
Purchase #4	$163.34	10.873%	$181.1	$181.10	$181.10	$181.10
Purchase #5	$74.71	4.171%	$77.8262	$77.83	$77.85	$77.80
Purchase #6	$148.62	12.458%	$167.1351	$167.14	$167.15	$167.10
Purchase #7	$80.67	11.601%	$90.0285	$90.03	$90.05	$90.00
7 purchase totals =	$781.25		$851.5503	$851.56	$851.60	$851.50