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	$97.52	10.803%	$108.0551	$108.06	$108.05	$108.10
Purchase #2	$133.33	3.644%	$138.1885	$138.19	$138.20	$138.20
Purchase #3	$78.46	8.206%	$84.8984	$84.90	$84.90	$84.90
Purchase #4	$119.90	6.229%	$127.3686	$127.37	$127.35	$127.40
Purchase #5	$210.37	9.131%	$229.5789	$229.58	$229.60	$229.60
Purchase #6	$168.83	7.648%	$181.7421	$181.74	$181.75	$181.70
Purchase #7	$70.35	11.696%	$78.5781	$78.58	$78.60	$78.60
7 purchase totals =	$878.76		$948.4097	$948.42	$948.45	$948.50