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	$118.40	7.729%	$127.5511	$127.55	$127.55	$127.60
Purchase #2	$129.95	6.164%	$137.9601	$137.96	$137.95	$138.00
Purchase #3	$66.76	6.376%	$71.0166	$71.02	$71.00	$71.00
Purchase #4	$94.44	5.241%	$99.3896	$99.39	$99.40	$99.40
Purchase #5	$29.41	13.671%	$33.4306	$33.43	$33.45	$33.40
Purchase #6	$160.37	7.484%	$172.3721	$172.37	$172.35	$172.40
Purchase #7	$189.81	7.661%	$204.3513	$204.35	$204.35	$204.40
7 purchase totals =	$789.14		$846.0714	$846.07	$846.05	$846.20