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	$33.55	10.453%	$37.057	$37.06	$37.05	$37.10
Purchase #2	$70.77	13.523%	$80.3402	$80.34	$80.35	$80.30
Purchase #3	$172.38	12.602%	$194.1033	$194.10	$194.10	$194.10
Purchase #4	$143.94	9.617%	$157.7827	$157.78	$157.80	$157.80
Purchase #5	$28.95	8.732%	$31.4779	$31.48	$31.50	$31.50
Purchase #6	$184.91	6.262%	$196.4891	$196.49	$196.50	$196.50
Purchase #7	$13.88	9.584%	$15.2103	$15.21	$15.20	$15.20
7 purchase totals =	$648.38		$712.4605	$712.46	$712.50	$712.50