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	$119.61	10.791%	$132.5171	$132.52	$132.50	$132.50
Purchase #2	$196.86	13.671%	$223.7727	$223.77	$223.75	$223.80
Purchase #3	$141.68	4.161%	$147.5753	$147.58	$147.60	$147.60
Purchase #4	$152.31	11.337%	$169.5774	$169.58	$169.60	$169.60
Purchase #5	$84.72	3.630%	$87.7953	$87.80	$87.80	$87.80
Purchase #6	$7.92	9.733%	$8.6909	$8.69	$8.70	$8.70
Purchase #7	$112.50	13.343%	$127.5109	$127.51	$127.50	$127.50
7 purchase totals =	$815.60		$897.4396	$897.45	$897.45	$897.50