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	$71.98	10.461%	$79.5098	$79.51	$79.50	$79.50
Purchase #2	$34.80	12.746%	$39.2356	$39.24	$39.25	$39.20
Purchase #3	$185.71	7.423%	$199.4953	$199.50	$199.50	$199.50
Purchase #4	$246.51	12.837%	$278.1545	$278.15	$278.15	$278.20
Purchase #5	$40.70	11.828%	$45.514	$45.51	$45.50	$45.50
Purchase #6	$196.93	13.113%	$222.7534	$222.75	$222.75	$222.80
Purchase #7	$192.64	3.617%	$199.6078	$199.61	$199.60	$199.60
7 purchase totals =	$969.27		$1,064.2704	$1,064.27	$1,064.25	$1,064.30