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	$161.78	7.669%	$174.1869	$174.19	$174.20	$174.20
Purchase #2	$78.70	10.565%	$87.0147	$87.01	$87.00	$87.00
Purchase #3	$213.70	11.318%	$237.8866	$237.89	$237.90	$237.90
Purchase #4	$38.85	3.219%	$40.1006	$40.10	$40.10	$40.10
Purchase #5	$243.66	4.792%	$255.3362	$255.34	$255.35	$255.30
Purchase #6	$117.29	7.858%	$126.5066	$126.51	$126.50	$126.50
Purchase #7	$150.68	10.748%	$166.8751	$166.88	$166.90	$166.90
7 purchase totals =	$1,004.66		$1,087.9067	$1,087.92	$1,087.95	$1,087.90