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	$56.72	13.378%	$64.308	$64.31	$64.30	$64.30
Purchase #2	$33.94	11.534%	$37.8546	$37.85	$37.85	$37.90
Purchase #3	$237.50	6.412%	$252.7285	$252.73	$252.75	$252.70
Purchase #4	$240.69	13.824%	$273.963	$273.96	$273.95	$274.00
Purchase #5	$162.43	12.597%	$182.8913	$182.89	$182.90	$182.90
Purchase #6	$142.99	6.768%	$152.6676	$152.67	$152.65	$152.70
Purchase #7	$146.30	8.420%	$158.6185	$158.62	$158.60	$158.60
7 purchase totals =	$1,020.57		$1,123.0315	$1,123.03	$1,123.00	$1,123.10