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	$64.50	11.756%	$72.0826	$72.08	$72.10	$72.10
Purchase #2	$114.58	6.228%	$121.716	$121.72	$121.70	$121.70
Purchase #3	$53.45	11.169%	$59.4198	$59.42	$59.40	$59.40
Purchase #4	$28.70	12.827%	$32.3813	$32.38	$32.40	$32.40
Purchase #5	$49.30	3.564%	$51.0571	$51.06	$51.05	$51.10
Purchase #6	$150.25	4.752%	$157.3899	$157.39	$157.40	$157.40
Purchase #7	$102.48	5.497%	$108.1133	$108.11	$108.10	$108.10
7 purchase totals =	$563.26		$602.1600	$602.16	$602.15	$602.20