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	$32.49	3.841%	$33.7379	$33.74	$33.75	$33.70
Purchase #2	$146.27	13.426%	$165.9082	$165.91	$165.90	$165.90
Purchase #3	$99.87	5.507%	$105.3698	$105.37	$105.35	$105.40
Purchase #4	$85.65	6.753%	$91.4339	$91.43	$91.45	$91.40
Purchase #5	$192.83	13.356%	$218.5844	$218.58	$218.60	$218.60
Purchase #6	$108.95	7.796%	$117.4437	$117.44	$117.45	$117.40
Purchase #7	$190.71	12.666%	$214.8653	$214.87	$214.85	$214.90
7 purchase totals =	$856.77		$947.3432	$947.34	$947.35	$947.30