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	$244.37	11.659%	$272.8611	$272.86	$272.85	$272.90
Purchase #2	$169.95	12.684%	$191.5065	$191.51	$191.50	$191.50
Purchase #3	$199.89	12.343%	$224.5624	$224.56	$224.55	$224.60
Purchase #4	$22.94	3.181%	$23.6697	$23.67	$23.65	$23.70
Purchase #5	$209.78	11.469%	$233.8397	$233.84	$233.85	$233.80
Purchase #6	$56.55	5.245%	$59.516	$59.52	$59.50	$59.50
Purchase #7	$146.71	8.326%	$158.9251	$158.93	$158.95	$158.90
7 purchase totals =	$1,050.19		$1,164.8805	$1,164.89	$1,164.85	$1,164.90