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	$155.78	7.475%	$167.4246	$167.42	$167.40	$167.40
Purchase #2	$246.30	6.482%	$262.2652	$262.27	$262.25	$262.30
Purchase #3	$25.84	5.802%	$27.3392	$27.34	$27.35	$27.30
Purchase #4	$113.51	7.850%	$122.4205	$122.42	$122.40	$122.40
Purchase #5	$127.32	4.705%	$133.3104	$133.31	$133.30	$133.30
Purchase #6	$69.58	3.565%	$72.0605	$72.06	$72.05	$72.10
Purchase #7	$92.98	8.121%	$100.5309	$100.53	$100.55	$100.50
7 purchase totals =	$831.31		$885.3513	$885.35	$885.30	$885.30