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	$174.97	4.325%	$182.5375	$182.54	$182.55	$182.50
Purchase #2	$79.33	8.192%	$85.8287	$85.83	$85.85	$85.80
Purchase #3	$115.27	9.816%	$126.5849	$126.58	$126.60	$126.60
Purchase #4	$244.80	4.338%	$255.4194	$255.42	$255.40	$255.40
Purchase #5	$226.79	6.742%	$242.0802	$242.08	$242.10	$242.10
Purchase #6	$127.66	9.358%	$139.6064	$139.61	$139.60	$139.60
Purchase #7	$81.41	5.680%	$86.0341	$86.03	$86.05	$86.00
7 purchase totals =	$1,050.23		$1,118.0912	$1,118.09	$1,118.15	$1,118.00