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	$141.72	11.474%	$157.981	$157.98	$158.00	$158.00
Purchase #2	$216.25	13.568%	$245.5908	$245.59	$245.60	$245.60
Purchase #3	$183.51	9.478%	$200.9031	$200.90	$200.90	$200.90
Purchase #4	$132.63	8.337%	$143.6874	$143.69	$143.70	$143.70
Purchase #5	$54.89	12.711%	$61.8671	$61.87	$61.85	$61.90
Purchase #6	$33.97	9.800%	$37.2991	$37.30	$37.30	$37.30
Purchase #7	$121.96	13.718%	$138.6905	$138.69	$138.70	$138.70
7 purchase totals =	$884.93		$986.0190	$986.02	$986.05	$986.10