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	$127.95	7.523%	$137.5757	$137.58	$137.60	$137.60
Purchase #2	$159.93	13.435%	$181.4166	$181.42	$181.40	$181.40
Purchase #3	$20.55	4.830%	$21.5426	$21.54	$21.55	$21.50
Purchase #4	$34.95	5.648%	$36.924	$36.92	$36.90	$36.90
Purchase #5	$185.83	3.245%	$191.8602	$191.86	$191.85	$191.90
Purchase #6	$10.67	12.569%	$12.0111	$12.01	$12.00	$12.00
Purchase #7	$166.44	6.301%	$176.9274	$176.93	$176.95	$176.90
7 purchase totals =	$706.32		$758.2576	$758.26	$758.25	$758.20