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	$163.70	11.135%	$181.928	$181.93	$181.95	$181.90
Purchase #2	$124.94	13.201%	$141.4333	$141.43	$141.45	$141.40
Purchase #3	$167.40	4.678%	$175.231	$175.23	$175.25	$175.20
Purchase #4	$237.30	7.669%	$255.4985	$255.50	$255.50	$255.50
Purchase #5	$74.63	11.325%	$83.0818	$83.08	$83.10	$83.10
Purchase #6	$48.43	12.695%	$54.5782	$54.58	$54.60	$54.60
Purchase #7	$199.81	10.632%	$221.0538	$221.05	$221.05	$221.10
7 purchase totals =	$1,016.21		$1,112.8046	$1,112.80	$1,112.90	$1,112.80