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	$55.55	11.640%	$62.016	$62.02	$62.00	$62.00
Purchase #2	$34.72	3.798%	$36.0387	$36.04	$36.05	$36.00
Purchase #3	$61.70	6.309%	$65.5927	$65.59	$65.60	$65.60
Purchase #4	$75.86	13.715%	$86.2642	$86.26	$86.25	$86.30
Purchase #5	$48.78	3.271%	$50.3756	$50.38	$50.40	$50.40
Purchase #6	$101.42	9.623%	$111.1796	$111.18	$111.20	$111.20
Purchase #7	$130.52	8.315%	$141.3727	$141.37	$141.35	$141.40
7 purchase totals =	$508.55		$552.8395	$552.84	$552.85	$552.90