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	$222.89	11.496%	$248.5134	$248.51	$248.50	$248.50
Purchase #2	$21.95	12.429%	$24.6782	$24.68	$24.70	$24.70
Purchase #3	$13.52	10.197%	$14.8986	$14.90	$14.90	$14.90
Purchase #4	$141.98	9.658%	$155.6924	$155.69	$155.70	$155.70
Purchase #5	$75.36	3.730%	$78.1709	$78.17	$78.15	$78.20
Purchase #6	$75.60	3.366%	$78.1447	$78.14	$78.15	$78.10
Purchase #7	$173.69	6.587%	$185.131	$185.13	$185.15	$185.10
7 purchase totals =	$724.99		$785.2292	$785.22	$785.25	$785.20