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	$167.59	8.255%	$181.4246	$181.42	$181.40	$181.40
Purchase #2	$169.59	10.121%	$186.7542	$186.75	$186.75	$186.80
Purchase #3	$97.43	8.656%	$105.8635	$105.86	$105.85	$105.90
Purchase #4	$38.50	9.539%	$42.1725	$42.17	$42.15	$42.20
Purchase #5	$218.74	12.860%	$246.87	$246.87	$246.85	$246.90
Purchase #6	$230.56	8.702%	$250.6233	$250.62	$250.60	$250.60
Purchase #7	$132.47	6.600%	$141.213	$141.21	$141.20	$141.20
7 purchase totals =	$1,054.88		$1,154.9211	$1,154.90	$1,154.80	$1,155.00