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	$181.78	4.336%	$189.662	$189.66	$189.65	$189.70
Purchase #2	$167.85	5.121%	$176.4456	$176.45	$176.45	$176.40
Purchase #3	$179.44	3.307%	$185.3741	$185.37	$185.35	$185.40
Purchase #4	$243.40	12.273%	$273.2725	$273.27	$273.25	$273.30
Purchase #5	$48.42	6.251%	$51.4467	$51.45	$51.45	$51.40
Purchase #6	$101.40	9.781%	$111.3179	$111.32	$111.30	$111.30
Purchase #7	$44.96	3.366%	$46.4734	$46.47	$46.45	$46.50
7 purchase totals =	$967.25		$1,033.9922	$1,033.99	$1,033.90	$1,034.00