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	$120.25	10.603%	$133.0001	$133.00	$133.00	$133.00
Purchase #2	$91.86	11.704%	$102.6113	$102.61	$102.60	$102.60
Purchase #3	$81.83	11.812%	$91.4958	$91.50	$91.50	$91.50
Purchase #4	$29.75	13.143%	$33.66	$33.66	$33.65	$33.70
Purchase #5	$176.39	10.223%	$194.4223	$194.42	$194.40	$194.40
Purchase #6	$76.72	11.318%	$85.4032	$85.40	$85.40	$85.40
Purchase #7	$169.90	11.197%	$188.9237	$188.92	$188.90	$188.90
7 purchase totals =	$746.70		$829.5164	$829.51	$829.45	$829.50