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	$83.61	3.666%	$86.6751	$86.68	$86.70	$86.70
Purchase #2	$165.90	7.605%	$178.5167	$178.52	$178.50	$178.50
Purchase #3	$22.44	13.783%	$25.5329	$25.53	$25.55	$25.50
Purchase #4	$65.46	10.584%	$72.3883	$72.39	$72.40	$72.40
Purchase #5	$154.55	4.450%	$161.4275	$161.43	$161.45	$161.40
Purchase #6	$195.68	13.663%	$222.4158	$222.42	$222.40	$222.40
Purchase #7	$182.65	3.636%	$189.2912	$189.29	$189.30	$189.30
7 purchase totals =	$870.29		$936.2475	$936.26	$936.30	$936.20