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	$41.79	9.307%	$45.6794	$45.68	$45.70	$45.70
Purchase #2	$118.29	5.719%	$125.055	$125.06	$125.05	$125.10
Purchase #3	$69.63	12.644%	$78.434	$78.43	$78.45	$78.40
Purchase #4	$240.96	5.849%	$255.0538	$255.05	$255.05	$255.10
Purchase #5	$182.47	3.840%	$189.4768	$189.48	$189.50	$189.50
Purchase #6	$50.92	10.189%	$56.1082	$56.11	$56.10	$56.10
Purchase #7	$151.59	4.591%	$158.5495	$158.55	$158.55	$158.50
7 purchase totals =	$855.65		$908.3567	$908.36	$908.40	$908.40