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	$163.45	11.243%	$181.8267	$181.83	$181.85	$181.80
Purchase #2	$86.27	3.759%	$89.5129	$89.51	$89.50	$89.50
Purchase #3	$42.93	12.439%	$48.2701	$48.27	$48.25	$48.30
Purchase #4	$178.50	6.673%	$190.4113	$190.41	$190.40	$190.40
Purchase #5	$211.85	7.469%	$227.6731	$227.67	$227.65	$227.70
Purchase #6	$155.65	7.780%	$167.7596	$167.76	$167.75	$167.80
Purchase #7	$24.97	8.151%	$27.0053	$27.01	$27.00	$27.00
7 purchase totals =	$863.62		$932.4590	$932.46	$932.40	$932.50