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	$119.79	11.164%	$133.1634	$133.16	$133.15	$133.20
Purchase #2	$9.90	5.317%	$10.4264	$10.43	$10.45	$10.40
Purchase #3	$31.52	9.820%	$34.6153	$34.62	$34.60	$34.60
Purchase #4	$64.52	10.620%	$71.372	$71.37	$71.35	$71.40
Purchase #5	$250.32	3.695%	$259.5693	$259.57	$259.55	$259.60
Purchase #6	$52.61	7.622%	$56.6199	$56.62	$56.60	$56.60
Purchase #7	$11.50	7.682%	$12.3834	$12.38	$12.40	$12.40
7 purchase totals =	$540.16		$578.1497	$578.15	$578.10	$578.20