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	$78.87	9.396%	$86.2806	$86.28	$86.30	$86.30
Purchase #2	$76.54	8.547%	$83.0819	$83.08	$83.10	$83.10
Purchase #3	$195.83	4.531%	$204.7031	$204.70	$204.70	$204.70
Purchase #4	$184.69	5.463%	$194.7796	$194.78	$194.80	$194.80
Purchase #5	$100.81	10.811%	$111.7086	$111.71	$111.70	$111.70
Purchase #6	$241.69	3.652%	$250.5165	$250.52	$250.50	$250.50
Purchase #7	$162.51	11.640%	$181.4262	$181.43	$181.45	$181.40
7 purchase totals =	$1,040.94		$1,112.4965	$1,112.50	$1,112.55	$1,112.50