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	$30.32	6.276%	$32.2229	$32.22	$32.20	$32.20
Purchase #2	$121.95	3.423%	$126.1243	$126.12	$126.10	$126.10
Purchase #3	$89.43	11.169%	$99.4184	$99.42	$99.40	$99.40
Purchase #4	$241.86	5.459%	$255.0631	$255.06	$255.05	$255.10
Purchase #5	$88.51	4.535%	$92.5239	$92.52	$92.50	$92.50
Purchase #6	$149.59	12.806%	$168.7465	$168.75	$168.75	$168.70
Purchase #7	$45.92	5.201%	$48.3083	$48.31	$48.30	$48.30
7 purchase totals =	$767.58		$822.4074	$822.40	$822.30	$822.30