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	$50.95	6.761%	$54.3947	$54.39	$54.40	$54.40
Purchase #2	$118.60	3.835%	$123.1483	$123.15	$123.15	$123.10
Purchase #3	$95.55	5.422%	$100.7307	$100.73	$100.75	$100.70
Purchase #4	$176.34	13.569%	$200.2676	$200.27	$200.25	$200.30
Purchase #5	$130.57	4.356%	$136.2576	$136.26	$136.25	$136.30
Purchase #6	$9.26	12.582%	$10.4251	$10.43	$10.45	$10.40
Purchase #7	$112.31	4.286%	$117.1236	$117.12	$117.10	$117.10
7 purchase totals =	$693.58		$742.3476	$742.35	$742.35	$742.30