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	$33.85	5.617%	$35.7514	$35.75	$35.75	$35.80
Purchase #2	$49.28	9.130%	$53.7793	$53.78	$53.80	$53.80
Purchase #3	$174.71	6.179%	$185.5053	$185.51	$185.50	$185.50
Purchase #4	$161.59	6.828%	$172.6234	$172.62	$172.60	$172.60
Purchase #5	$43.81	12.427%	$49.2543	$49.25	$49.25	$49.30
Purchase #6	$43.65	5.852%	$46.2044	$46.20	$46.20	$46.20
Purchase #7	$167.43	5.130%	$176.0192	$176.02	$176.00	$176.00
7 purchase totals =	$674.32		$719.1373	$719.13	$719.10	$719.20