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	$245.60	11.436%	$273.6868	$273.69	$273.70	$273.70
Purchase #2	$218.95	7.172%	$234.6531	$234.65	$234.65	$234.70
Purchase #3	$152.90	3.370%	$158.0527	$158.05	$158.05	$158.10
Purchase #4	$116.70	3.298%	$120.5488	$120.55	$120.55	$120.50
Purchase #5	$100.69	10.495%	$111.2574	$111.26	$111.25	$111.30
Purchase #6	$12.47	5.378%	$13.1406	$13.14	$13.15	$13.10
Purchase #7	$87.35	10.127%	$96.1959	$96.20	$96.20	$96.20
7 purchase totals =	$934.66		$1,007.5353	$1,007.54	$1,007.55	$1,007.60