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	$176.86	12.299%	$198.612	$198.61	$198.60	$198.60
Purchase #2	$216.34	6.507%	$230.4172	$230.42	$230.40	$230.40
Purchase #3	$102.27	9.238%	$111.7177	$111.72	$111.70	$111.70
Purchase #4	$102.73	9.255%	$112.2377	$112.24	$112.25	$112.20
Purchase #5	$31.33	13.330%	$35.5063	$35.51	$35.50	$35.50
Purchase #6	$229.68	9.389%	$251.2447	$251.24	$251.25	$251.20
Purchase #7	$147.88	12.277%	$166.0352	$166.04	$166.05	$166.00
7 purchase totals =	$1,007.09		$1,105.7708	$1,105.78	$1,105.75	$1,105.60