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	$87.90	9.253%	$96.0334	$96.03	$96.05	$96.00
Purchase #2	$52.38	12.853%	$59.1124	$59.11	$59.10	$59.10
Purchase #3	$69.29	13.720%	$78.7966	$78.80	$78.80	$78.80
Purchase #4	$230.62	7.620%	$248.1932	$248.19	$248.20	$248.20
Purchase #5	$23.98	3.670%	$24.8601	$24.86	$24.85	$24.90
Purchase #6	$157.44	11.115%	$174.9395	$174.94	$174.95	$174.90
Purchase #7	$123.43	13.112%	$139.6141	$139.61	$139.60	$139.60
7 purchase totals =	$745.04		$821.5493	$821.54	$821.55	$821.50