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	$117.73	10.610%	$130.2212	$130.22	$130.20	$130.20
Purchase #2	$169.91	7.423%	$182.5224	$182.52	$182.50	$182.50
Purchase #3	$182.55	4.485%	$190.7374	$190.74	$190.75	$190.70
Purchase #4	$111.77	13.844%	$127.2434	$127.24	$127.25	$127.20
Purchase #5	$42.40	6.449%	$45.1344	$45.13	$45.15	$45.10
Purchase #6	$123.62	7.377%	$132.7394	$132.74	$132.75	$132.70
Purchase #7	$87.28	5.579%	$92.1494	$92.15	$92.15	$92.10
7 purchase totals =	$835.26		$900.7476	$900.74	$900.75	$900.50