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	$145.42	13.206%	$164.6242	$164.62	$164.60	$164.60
Purchase #2	$220.77	4.721%	$231.1926	$231.19	$231.20	$231.20
Purchase #3	$156.43	11.477%	$174.3835	$174.38	$174.40	$174.40
Purchase #4	$82.99	13.336%	$94.0575	$94.06	$94.05	$94.10
Purchase #5	$96.37	4.354%	$100.5659	$100.57	$100.55	$100.60
Purchase #6	$123.97	12.169%	$139.0559	$139.06	$139.05	$139.10
Purchase #7	$145.61	12.847%	$164.3165	$164.32	$164.30	$164.30
7 purchase totals =	$971.56		$1,068.1961	$1,068.20	$1,068.15	$1,068.30