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	$151.52	9.826%	$166.4084	$166.41	$166.40	$166.40
Purchase #2	$240.32	4.128%	$250.2404	$250.24	$250.25	$250.20
Purchase #3	$181.25	11.156%	$201.4703	$201.47	$201.45	$201.50
Purchase #4	$92.90	7.769%	$100.1174	$100.12	$100.10	$100.10
Purchase #5	$7.42	4.577%	$7.7596	$7.76	$7.75	$7.80
Purchase #6	$173.96	4.806%	$182.3205	$182.32	$182.30	$182.30
Purchase #7	$208.39	9.418%	$228.0162	$228.02	$228.00	$228.00
7 purchase totals =	$1,055.76		$1,136.3328	$1,136.34	$1,136.25	$1,136.30