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	$102.67	3.141%	$105.8949	$105.89	$105.90	$105.90
Purchase #2	$68.52	4.528%	$71.6226	$71.62	$71.60	$71.60
Purchase #3	$54.89	7.634%	$59.0803	$59.08	$59.10	$59.10
Purchase #4	$33.45	13.716%	$38.038	$38.04	$38.05	$38.00
Purchase #5	$153.85	6.560%	$163.9426	$163.94	$163.95	$163.90
Purchase #6	$236.99	10.459%	$261.7768	$261.78	$261.80	$261.80
Purchase #7	$163.41	4.796%	$171.2471	$171.25	$171.25	$171.20
7 purchase totals =	$813.78		$871.6023	$871.60	$871.65	$871.50