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	$243.55	6.448%	$259.2541	$259.25	$259.25	$259.30
Purchase #2	$210.35	8.308%	$227.8259	$227.83	$227.85	$227.80
Purchase #3	$32.31	11.326%	$35.9694	$35.97	$35.95	$36.00
Purchase #4	$224.88	5.153%	$236.4681	$236.47	$236.45	$236.50
Purchase #5	$91.72	7.461%	$98.5632	$98.56	$98.55	$98.60
Purchase #6	$98.52	7.132%	$105.5464	$105.55	$105.55	$105.50
Purchase #7	$121.83	10.660%	$134.8171	$134.82	$134.80	$134.80
7 purchase totals =	$1,023.16		$1,098.4442	$1,098.45	$1,098.40	$1,098.50