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	$200.40	10.552%	$221.5462	$221.55	$221.55	$221.50
Purchase #2	$158.91	5.777%	$168.0902	$168.09	$168.10	$168.10
Purchase #3	$231.73	12.709%	$261.1806	$261.18	$261.20	$261.20
Purchase #4	$137.86	4.510%	$144.0775	$144.08	$144.10	$144.10
Purchase #5	$155.77	12.146%	$174.6898	$174.69	$174.70	$174.70
Purchase #6	$58.38	7.706%	$62.8788	$62.88	$62.90	$62.90
Purchase #7	$228.39	4.420%	$238.4848	$238.48	$238.50	$238.50
7 purchase totals =	$1,171.44		$1,270.9479	$1,270.95	$1,271.05	$1,271.00