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	$165.42	4.332%	$172.586	$172.59	$172.60	$172.60
Purchase #2	$182.28	7.847%	$196.5835	$196.58	$196.60	$196.60
Purchase #3	$217.86	11.300%	$242.4782	$242.48	$242.50	$242.50
Purchase #4	$148.67	9.815%	$163.262	$163.26	$163.25	$163.30
Purchase #5	$250.29	8.840%	$272.4156	$272.42	$272.40	$272.40
Purchase #6	$190.25	4.631%	$199.0605	$199.06	$199.05	$199.10
Purchase #7	$224.27	6.328%	$238.4618	$238.46	$238.45	$238.50
7 purchase totals =	$1,379.04		$1,484.8476	$1,484.85	$1,484.85	$1,485.00