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	$142.89	3.257%	$147.5439	$147.54	$147.55	$147.50
Purchase #2	$227.83	12.176%	$255.5706	$255.57	$255.55	$255.60
Purchase #3	$161.29	7.730%	$173.7577	$173.76	$173.75	$173.80
Purchase #4	$202.89	12.606%	$228.4663	$228.47	$228.45	$228.50
Purchase #5	$185.46	11.603%	$206.9789	$206.98	$207.00	$207.00
Purchase #6	$181.88	10.421%	$200.8337	$200.83	$200.85	$200.80
Purchase #7	$242.26	8.742%	$263.4384	$263.44	$263.45	$263.40
7 purchase totals =	$1,344.50		$1,476.5895	$1,476.59	$1,476.60	$1,476.60