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	$108.59	10.192%	$119.6575	$119.66	$119.65	$119.70
Purchase #2	$154.98	11.156%	$172.2696	$172.27	$172.25	$172.30
Purchase #3	$207.71	10.482%	$229.4822	$229.48	$229.50	$229.50
Purchase #4	$246.89	12.676%	$278.1858	$278.19	$278.20	$278.20
Purchase #5	$129.80	13.575%	$147.4204	$147.42	$147.40	$147.40
Purchase #6	$48.49	6.109%	$51.4523	$51.45	$51.45	$51.50
Purchase #7	$20.29	3.475%	$20.9951	$21.00	$21.00	$21.00
7 purchase totals =	$916.75		$1,019.4629	$1,019.47	$1,019.45	$1,019.60