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	$119.44	3.642%	$123.79	$123.79	$123.80	$123.80
Purchase #2	$142.88	10.758%	$158.251	$158.25	$158.25	$158.30
Purchase #3	$35.92	8.190%	$38.8618	$38.86	$38.85	$38.90
Purchase #4	$31.44	6.300%	$33.4207	$33.42	$33.40	$33.40
Purchase #5	$140.60	11.719%	$157.0769	$157.08	$157.10	$157.10
Purchase #6	$216.98	11.183%	$241.2449	$241.24	$241.25	$241.20
Purchase #7	$156.90	10.571%	$173.4859	$173.49	$173.50	$173.50
7 purchase totals =	$844.16		$926.1312	$926.13	$926.15	$926.20