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	$181.67	3.779%	$188.5353	$188.54	$188.55	$188.50
Purchase #2	$24.63	11.677%	$27.506	$27.51	$27.50	$27.50
Purchase #3	$109.84	5.848%	$116.2634	$116.26	$116.25	$116.30
Purchase #4	$78.46	11.462%	$87.4531	$87.45	$87.45	$87.50
Purchase #5	$78.46	9.852%	$86.1899	$86.19	$86.20	$86.20
Purchase #6	$13.33	9.137%	$14.548	$14.55	$14.55	$14.50
Purchase #7	$95.67	10.714%	$105.9201	$105.92	$105.90	$105.90
7 purchase totals =	$582.06		$626.4158	$626.42	$626.40	$626.40