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	$140.34	3.733%	$145.5789	$145.58	$145.60	$145.60
Purchase #2	$42.47	6.522%	$45.2399	$45.24	$45.25	$45.20
Purchase #3	$27.27	8.490%	$29.5852	$29.59	$29.60	$29.60
Purchase #4	$82.46	5.422%	$86.931	$86.93	$86.95	$86.90
Purchase #5	$240.32	5.564%	$253.6914	$253.69	$253.70	$253.70
Purchase #6	$97.53	7.711%	$105.0505	$105.05	$105.05	$105.10
Purchase #7	$113.96	11.806%	$127.4141	$127.41	$127.40	$127.40
7 purchase totals =	$744.35		$793.4910	$793.49	$793.55	$793.50