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	$219.68	9.827%	$241.268	$241.27	$241.25	$241.30
Purchase #2	$95.29	5.700%	$100.7215	$100.72	$100.70	$100.70
Purchase #3	$222.46	7.483%	$239.1067	$239.11	$239.10	$239.10
Purchase #4	$149.27	4.289%	$155.6722	$155.67	$155.65	$155.70
Purchase #5	$108.44	3.511%	$112.2473	$112.25	$112.25	$112.20
Purchase #6	$87.31	9.689%	$95.7695	$95.77	$95.75	$95.80
Purchase #7	$50.45	8.437%	$54.7065	$54.71	$54.70	$54.70
7 purchase totals =	$932.90		$999.4917	$999.50	$999.40	$999.50