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	$159.39	5.838%	$168.6952	$168.70	$168.70	$168.70
Purchase #2	$202.35	5.560%	$213.6007	$213.60	$213.60	$213.60
Purchase #3	$224.42	13.308%	$254.2858	$254.29	$254.30	$254.30
Purchase #4	$144.73	13.730%	$164.6014	$164.60	$164.60	$164.60
Purchase #5	$59.95	11.255%	$66.6974	$66.70	$66.70	$66.70
Purchase #6	$136.96	4.107%	$142.5849	$142.58	$142.60	$142.60
Purchase #7	$31.78	12.552%	$35.769	$35.77	$35.75	$35.80
7 purchase totals =	$959.58		$1,046.2344	$1,046.24	$1,046.25	$1,046.30