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	$139.32	7.722%	$150.0783	$150.08	$150.10	$150.10
Purchase #2	$177.64	7.472%	$190.9133	$190.91	$190.90	$190.90
Purchase #3	$79.39	5.320%	$83.6135	$83.61	$83.60	$83.60
Purchase #4	$242.70	12.295%	$272.54	$272.54	$272.55	$272.50
Purchase #5	$208.86	4.863%	$219.0169	$219.02	$219.00	$219.00
Purchase #6	$130.85	6.725%	$139.6497	$139.65	$139.65	$139.60
Purchase #7	$158.59	5.507%	$167.3236	$167.32	$167.30	$167.30
7 purchase totals =	$1,137.35		$1,223.1353	$1,223.13	$1,223.10	$1,223.00