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	$216.72	8.193%	$234.4759	$234.48	$234.50	$234.50
Purchase #2	$103.50	13.616%	$117.5926	$117.59	$117.60	$117.60
Purchase #3	$241.98	4.210%	$252.1674	$252.17	$252.15	$252.20
Purchase #4	$67.38	9.214%	$73.5884	$73.59	$73.60	$73.60
Purchase #5	$161.76	12.752%	$182.3876	$182.39	$182.40	$182.40
Purchase #6	$38.54	13.192%	$43.6242	$43.62	$43.60	$43.60
Purchase #7	$169.35	10.109%	$186.4696	$186.47	$186.45	$186.50
7 purchase totals =	$999.23		$1,090.3057	$1,090.31	$1,090.30	$1,090.40