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	$148.38	5.686%	$156.8169	$156.82	$156.80	$156.80
Purchase #2	$84.65	5.336%	$89.1669	$89.17	$89.15	$89.20
Purchase #3	$120.84	5.437%	$127.4101	$127.41	$127.40	$127.40
Purchase #4	$71.67	11.639%	$80.0117	$80.01	$80.00	$80.00
Purchase #5	$128.51	13.462%	$145.81	$145.81	$145.80	$145.80
Purchase #6	$231.56	8.137%	$250.402	$250.40	$250.40	$250.40
Purchase #7	$249.37	13.512%	$283.0649	$283.06	$283.05	$283.10
7 purchase totals =	$1,034.98		$1,132.6825	$1,132.68	$1,132.60	$1,132.70