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	$136.49	10.757%	$151.1722	$151.17	$151.15	$151.20
Purchase #2	$205.29	10.523%	$226.8927	$226.89	$226.90	$226.90
Purchase #3	$160.89	7.307%	$172.6462	$172.65	$172.65	$172.60
Purchase #4	$162.95	3.107%	$168.0129	$168.01	$168.00	$168.00
Purchase #5	$40.68	3.839%	$42.2417	$42.24	$42.25	$42.20
Purchase #6	$166.49	11.120%	$185.0037	$185.00	$185.00	$185.00
Purchase #7	$107.42	11.283%	$119.5402	$119.54	$119.55	$119.50
7 purchase totals =	$980.21		$1,065.5096	$1,065.50	$1,065.50	$1,065.40