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	$82.79	11.438%	$92.2595	$92.26	$92.25	$92.30
Purchase #2	$134.97	4.164%	$140.5902	$140.59	$140.60	$140.60
Purchase #3	$63.32	3.723%	$65.6774	$65.68	$65.70	$65.70
Purchase #4	$78.96	4.248%	$82.3142	$82.31	$82.30	$82.30
Purchase #5	$57.81	5.806%	$61.1664	$61.17	$61.15	$61.20
Purchase #6	$26.95	5.480%	$28.4269	$28.43	$28.45	$28.40
Purchase #7	$160.49	11.849%	$179.5065	$179.51	$179.50	$179.50
7 purchase totals =	$605.29		$649.9411	$649.95	$649.95	$650.00