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	$162.74	13.780%	$185.1656	$185.17	$185.15	$185.20
Purchase #2	$214.71	13.257%	$243.1741	$243.17	$243.15	$243.20
Purchase #3	$45.25	6.462%	$48.1741	$48.17	$48.15	$48.20
Purchase #4	$44.79	12.223%	$50.2647	$50.26	$50.25	$50.30
Purchase #5	$234.53	11.187%	$260.7669	$260.77	$260.75	$260.80
Purchase #6	$111.59	4.342%	$116.4352	$116.44	$116.45	$116.40
Purchase #7	$205.68	11.125%	$228.5619	$228.56	$228.55	$228.60
7 purchase totals =	$1,019.29		$1,132.5425	$1,132.54	$1,132.45	$1,132.70