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	$92.59	4.316%	$96.5862	$96.59	$96.60	$96.60
Purchase #2	$64.51	3.457%	$66.7401	$66.74	$66.75	$66.70
Purchase #3	$210.56	10.464%	$232.593	$232.59	$232.60	$232.60
Purchase #4	$142.38	9.569%	$156.0043	$156.00	$156.00	$156.00
Purchase #5	$13.82	13.669%	$15.7091	$15.71	$15.70	$15.70
Purchase #6	$64.63	11.704%	$72.1943	$72.19	$72.20	$72.20
Purchase #7	$237.34	9.505%	$259.8992	$259.90	$259.90	$259.90
7 purchase totals =	$825.83		$899.7262	$899.72	$899.75	$899.70