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	$164.89	10.658%	$182.464	$182.46	$182.45	$182.50
Purchase #2	$215.31	10.806%	$238.5764	$238.58	$238.60	$238.60
Purchase #3	$154.38	4.682%	$161.6081	$161.61	$161.60	$161.60
Purchase #4	$202.72	7.455%	$217.8328	$217.83	$217.85	$217.80
Purchase #5	$77.70	11.819%	$86.8834	$86.88	$86.90	$86.90
Purchase #6	$158.79	8.716%	$172.6301	$172.63	$172.65	$172.60
Purchase #7	$55.39	4.643%	$57.9618	$57.96	$57.95	$58.00
7 purchase totals =	$1,029.18		$1,117.9566	$1,117.95	$1,118.00	$1,118.00