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	$228.45	12.148%	$256.2021	$256.20	$256.20	$256.20
Purchase #2	$222.31	13.629%	$252.6086	$252.61	$252.60	$252.60
Purchase #3	$177.77	5.134%	$186.8967	$186.90	$186.90	$186.90
Purchase #4	$162.98	8.505%	$176.8414	$176.84	$176.85	$176.80
Purchase #5	$217.96	10.507%	$240.8611	$240.86	$240.85	$240.90
Purchase #6	$105.40	6.565%	$112.3195	$112.32	$112.30	$112.30
Purchase #7	$98.35	13.766%	$111.8889	$111.89	$111.90	$111.90
7 purchase totals =	$1,213.22		$1,337.6183	$1,337.62	$1,337.60	$1,337.60