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	$137.28	3.141%	$141.592	$141.59	$141.60	$141.60
Purchase #2	$43.93	3.592%	$45.508	$45.51	$45.50	$45.50
Purchase #3	$46.47	12.341%	$52.2049	$52.20	$52.20	$52.20
Purchase #4	$114.56	3.188%	$118.2122	$118.21	$118.20	$118.20
Purchase #5	$167.64	7.361%	$179.98	$179.98	$180.00	$180.00
Purchase #6	$242.83	5.795%	$256.902	$256.90	$256.90	$256.90
Purchase #7	$43.62	11.827%	$48.7789	$48.78	$48.80	$48.80
7 purchase totals =	$796.33		$843.1780	$843.17	$843.20	$843.20