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	$80.49	7.411%	$86.4551	$86.46	$86.45	$86.50
Purchase #2	$78.89	6.510%	$84.0257	$84.03	$84.05	$84.00
Purchase #3	$78.96	8.854%	$85.9511	$85.95	$85.95	$86.00
Purchase #4	$121.66	13.307%	$137.8493	$137.85	$137.85	$137.80
Purchase #5	$227.47	4.548%	$237.8153	$237.82	$237.80	$237.80
Purchase #6	$152.92	12.797%	$172.4892	$172.49	$172.50	$172.50
Purchase #7	$91.34	8.689%	$99.2765	$99.28	$99.30	$99.30
7 purchase totals =	$831.73		$903.8622	$903.88	$903.90	$903.90