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	$133.57	12.570%	$150.3597	$150.36	$150.35	$150.40
Purchase #2	$108.37	4.327%	$113.0592	$113.06	$113.05	$113.10
Purchase #3	$16.92	11.303%	$18.8325	$18.83	$18.85	$18.80
Purchase #4	$27.25	10.598%	$30.138	$30.14	$30.15	$30.10
Purchase #5	$45.86	3.113%	$47.2876	$47.29	$47.30	$47.30
Purchase #6	$65.53	11.745%	$73.2265	$73.23	$73.25	$73.20
Purchase #7	$93.89	7.184%	$100.6351	$100.64	$100.65	$100.60
7 purchase totals =	$491.39		$533.5386	$533.55	$533.60	$533.50