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	$208.95	6.796%	$223.1502	$223.15	$223.15	$223.20
Purchase #2	$103.54	4.205%	$107.8939	$107.89	$107.90	$107.90
Purchase #3	$118.81	6.487%	$126.5172	$126.52	$126.50	$126.50
Purchase #4	$105.90	10.239%	$116.7431	$116.74	$116.75	$116.70
Purchase #5	$239.36	6.796%	$255.6269	$255.63	$255.65	$255.60
Purchase #6	$181.76	9.180%	$198.4456	$198.45	$198.45	$198.40
Purchase #7	$84.81	12.334%	$95.2705	$95.27	$95.25	$95.30
7 purchase totals =	$1,043.13		$1,123.6474	$1,123.65	$1,123.65	$1,123.60