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	$161.62	12.604%	$181.9906	$181.99	$182.00	$182.00
Purchase #2	$91.84	13.142%	$103.9096	$103.91	$103.90	$103.90
Purchase #3	$75.81	3.509%	$78.4702	$78.47	$78.45	$78.50
Purchase #4	$208.90	7.479%	$224.5236	$224.52	$224.50	$224.50
Purchase #5	$43.86	4.681%	$45.9131	$45.91	$45.90	$45.90
Purchase #6	$238.79	13.170%	$270.2386	$270.24	$270.25	$270.20
Purchase #7	$27.70	12.544%	$31.1747	$31.17	$31.15	$31.20
7 purchase totals =	$848.52		$936.2204	$936.21	$936.15	$936.20