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	$164.60	4.106%	$171.3585	$171.36	$171.35	$171.40
Purchase #2	$119.61	5.662%	$126.3823	$126.38	$126.40	$126.40
Purchase #3	$142.32	9.766%	$156.219	$156.22	$156.20	$156.20
Purchase #4	$112.97	9.150%	$123.3068	$123.31	$123.30	$123.30
Purchase #5	$47.71	13.374%	$54.0907	$54.09	$54.10	$54.10
Purchase #6	$228.46	10.315%	$252.0256	$252.03	$252.05	$252.00
Purchase #7	$154.88	11.385%	$172.5131	$172.51	$172.50	$172.50
7 purchase totals =	$970.55		$1,055.8960	$1,055.90	$1,055.90	$1,055.90