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	$140.80	7.525%	$151.3952	$151.40	$151.40	$151.40
Purchase #2	$153.56	7.523%	$165.1123	$165.11	$165.10	$165.10
Purchase #3	$91.95	10.223%	$101.35	$101.35	$101.35	$101.40
Purchase #4	$53.85	6.693%	$57.4542	$57.45	$57.45	$57.50
Purchase #5	$38.55	5.176%	$40.5453	$40.55	$40.55	$40.50
Purchase #6	$98.60	9.704%	$108.1681	$108.17	$108.15	$108.20
Purchase #7	$223.38	3.696%	$231.6361	$231.64	$231.65	$231.60
7 purchase totals =	$800.69		$855.6612	$855.67	$855.65	$855.70