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	$215.31	10.274%	$237.4309	$237.43	$237.45	$237.40
Purchase #2	$57.70	4.262%	$60.1592	$60.16	$60.15	$60.20
Purchase #3	$98.98	12.274%	$111.1288	$111.13	$111.15	$111.10
Purchase #4	$98.29	13.660%	$111.7164	$111.72	$111.70	$111.70
Purchase #5	$165.44	8.426%	$179.38	$179.38	$179.40	$179.40
Purchase #6	$154.42	10.412%	$170.4982	$170.50	$170.50	$170.50
Purchase #7	$73.98	5.676%	$78.1791	$78.18	$78.20	$78.20
7 purchase totals =	$864.12		$948.4926	$948.50	$948.55	$948.50