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	$45.99	13.229%	$52.074	$52.07	$52.05	$52.10
Purchase #2	$237.61	12.230%	$266.6697	$266.67	$266.65	$266.70
Purchase #3	$101.93	3.600%	$105.5995	$105.60	$105.60	$105.60
Purchase #4	$164.42	12.816%	$185.4921	$185.49	$185.50	$185.50
Purchase #5	$162.70	9.160%	$177.6033	$177.60	$177.60	$177.60
Purchase #6	$49.79	5.842%	$52.6987	$52.70	$52.70	$52.70
Purchase #7	$216.36	11.518%	$241.2803	$241.28	$241.30	$241.30
7 purchase totals =	$978.80		$1,081.4176	$1,081.41	$1,081.40	$1,081.50