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	$41.71	8.455%	$45.2366	$45.24	$45.25	$45.20
Purchase #2	$49.75	8.296%	$53.8773	$53.88	$53.90	$53.90
Purchase #3	$121.84	13.153%	$137.8656	$137.87	$137.85	$137.90
Purchase #4	$118.76	6.506%	$126.4865	$126.49	$126.50	$126.50
Purchase #5	$165.31	13.345%	$187.3706	$187.37	$187.35	$187.40
Purchase #6	$92.29	11.723%	$103.1092	$103.11	$103.10	$103.10
Purchase #7	$36.89	5.599%	$38.9555	$38.96	$38.95	$39.00
7 purchase totals =	$626.55		$692.9013	$692.92	$692.90	$693.00