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	$57.78	12.831%	$65.1938	$65.19	$65.20	$65.20
Purchase #2	$130.93	13.419%	$148.4995	$148.50	$148.50	$148.50
Purchase #3	$49.81	7.211%	$53.4018	$53.40	$53.40	$53.40
Purchase #4	$135.70	4.360%	$141.6165	$141.62	$141.60	$141.60
Purchase #5	$141.67	11.788%	$158.3701	$158.37	$158.35	$158.40
Purchase #6	$82.43	11.857%	$92.2037	$92.20	$92.20	$92.20
Purchase #7	$128.34	13.767%	$146.0086	$146.01	$146.00	$146.00
7 purchase totals =	$726.66		$805.2940	$805.29	$805.25	$805.30