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	$60.98	3.766%	$63.2765	$63.28	$63.30	$63.30
Purchase #2	$59.69	9.281%	$65.2298	$65.23	$65.25	$65.20
Purchase #3	$224.88	13.781%	$255.8707	$255.87	$255.85	$255.90
Purchase #4	$95.56	13.317%	$108.2857	$108.29	$108.30	$108.30
Purchase #5	$20.37	6.112%	$21.615	$21.62	$21.60	$21.60
Purchase #6	$51.40	13.320%	$58.2465	$58.25	$58.25	$58.20
Purchase #7	$203.39	5.240%	$214.0476	$214.05	$214.05	$214.00
7 purchase totals =	$716.27		$786.5718	$786.59	$786.60	$786.50