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	$246.38	5.550%	$260.0541	$260.05	$260.05	$260.10
Purchase #2	$148.57	3.481%	$153.7417	$153.74	$153.75	$153.70
Purchase #3	$13.88	12.386%	$15.5992	$15.60	$15.60	$15.60
Purchase #4	$65.90	10.254%	$72.6574	$72.66	$72.65	$72.70
Purchase #5	$7.34	3.426%	$7.5915	$7.59	$7.60	$7.60
Purchase #6	$153.45	11.713%	$171.4236	$171.42	$171.40	$171.40
Purchase #7	$171.25	8.518%	$185.8371	$185.84	$185.85	$185.80
7 purchase totals =	$806.77		$866.9046	$866.90	$866.90	$866.90