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	$157.79	13.514%	$179.1137	$179.11	$179.10	$179.10
Purchase #2	$69.56	4.294%	$72.5469	$72.55	$72.55	$72.50
Purchase #3	$102.80	13.338%	$116.5115	$116.51	$116.50	$116.50
Purchase #4	$127.93	13.771%	$145.5472	$145.55	$145.55	$145.50
Purchase #5	$50.28	13.202%	$56.918	$56.92	$56.90	$56.90
Purchase #6	$119.51	10.678%	$132.2713	$132.27	$132.25	$132.30
Purchase #7	$177.67	10.114%	$195.6395	$195.64	$195.65	$195.60
7 purchase totals =	$805.54		$898.5481	$898.55	$898.50	$898.40