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	$103.86	6.357%	$110.4624	$110.46	$110.45	$110.50
Purchase #2	$120.42	5.669%	$127.2466	$127.25	$127.25	$127.20
Purchase #3	$182.80	7.351%	$196.2376	$196.24	$196.25	$196.20
Purchase #4	$146.82	12.116%	$164.6087	$164.61	$164.60	$164.60
Purchase #5	$176.56	9.434%	$193.2167	$193.22	$193.20	$193.20
Purchase #6	$169.42	9.859%	$186.1231	$186.12	$186.10	$186.10
Purchase #7	$13.64	12.510%	$15.3464	$15.35	$15.35	$15.30
7 purchase totals =	$913.52		$993.2415	$993.25	$993.20	$993.10