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	$177.99	7.501%	$191.341	$191.34	$191.35	$191.30
Purchase #2	$149.90	7.746%	$161.5113	$161.51	$161.50	$161.50
Purchase #3	$29.88	13.429%	$33.8926	$33.89	$33.90	$33.90
Purchase #4	$100.76	10.403%	$111.2421	$111.24	$111.25	$111.20
Purchase #5	$15.77	6.450%	$16.7872	$16.79	$16.80	$16.80
Purchase #6	$134.26	7.443%	$144.253	$144.25	$144.25	$144.30
Purchase #7	$241.31	5.198%	$253.8533	$253.85	$253.85	$253.90
7 purchase totals =	$849.87		$912.8805	$912.87	$912.90	$912.90