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	$148.75	10.821%	$164.8462	$164.85	$164.85	$164.80
Purchase #2	$129.33	11.634%	$144.3763	$144.38	$144.40	$144.40
Purchase #3	$53.29	5.712%	$56.3339	$56.33	$56.35	$56.30
Purchase #4	$18.60	9.275%	$20.3252	$20.33	$20.35	$20.30
Purchase #5	$80.27	7.133%	$85.9957	$86.00	$86.00	$86.00
Purchase #6	$111.75	9.622%	$122.5026	$122.50	$122.50	$122.50
Purchase #7	$222.94	10.156%	$245.5818	$245.58	$245.60	$245.60
7 purchase totals =	$764.93		$839.9617	$839.97	$840.05	$839.90