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	$167.29	4.874%	$175.4437	$175.44	$175.45	$175.40
Purchase #2	$41.29	5.317%	$43.4854	$43.49	$43.50	$43.50
Purchase #3	$114.69	7.850%	$123.6932	$123.69	$123.70	$123.70
Purchase #4	$68.27	10.721%	$75.5892	$75.59	$75.60	$75.60
Purchase #5	$58.82	7.135%	$63.0168	$63.02	$63.00	$63.00
Purchase #6	$133.31	7.534%	$143.3536	$143.35	$143.35	$143.40
Purchase #7	$38.82	9.603%	$42.5479	$42.55	$42.55	$42.50
7 purchase totals =	$622.49		$667.1298	$667.13	$667.15	$667.10