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	$237.40	3.597%	$245.9393	$245.94	$245.95	$245.90
Purchase #2	$132.55	3.743%	$137.5113	$137.51	$137.50	$137.50
Purchase #3	$27.39	5.182%	$28.8093	$28.81	$28.80	$28.80
Purchase #4	$149.50	3.763%	$155.1257	$155.13	$155.15	$155.10
Purchase #5	$13.77	12.517%	$15.4936	$15.49	$15.50	$15.50
Purchase #6	$150.27	8.370%	$162.8476	$162.85	$162.85	$162.80
Purchase #7	$19.85	4.644%	$20.7718	$20.77	$20.75	$20.80
7 purchase totals =	$730.73		$766.4986	$766.50	$766.50	$766.40