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	$114.57	6.143%	$121.608	$121.61	$121.60	$121.60
Purchase #2	$84.50	3.693%	$87.6206	$87.62	$87.60	$87.60
Purchase #3	$57.42	3.429%	$59.3889	$59.39	$59.40	$59.40
Purchase #4	$35.81	7.782%	$38.5967	$38.60	$38.60	$38.60
Purchase #5	$61.94	7.736%	$66.7317	$66.73	$66.75	$66.70
Purchase #6	$69.70	4.386%	$72.757	$72.76	$72.75	$72.80
Purchase #7	$36.25	7.384%	$38.9267	$38.93	$38.95	$38.90
7 purchase totals =	$460.19		$485.6296	$485.64	$485.65	$485.60