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	$171.77	6.136%	$182.3098	$182.31	$182.30	$182.30
Purchase #2	$103.58	9.474%	$113.3932	$113.39	$113.40	$113.40
Purchase #3	$59.38	7.168%	$63.6364	$63.64	$63.65	$63.60
Purchase #4	$210.56	8.689%	$228.8556	$228.86	$228.85	$228.90
Purchase #5	$60.39	7.721%	$65.0527	$65.05	$65.05	$65.10
Purchase #6	$13.96	10.499%	$15.4257	$15.43	$15.45	$15.40
Purchase #7	$80.25	6.478%	$85.4486	$85.45	$85.45	$85.40
7 purchase totals =	$699.89		$754.1220	$754.13	$754.15	$754.10