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	$178.67	11.162%	$198.6131	$198.61	$198.60	$198.60
Purchase #2	$127.45	12.497%	$143.3774	$143.38	$143.40	$143.40
Purchase #3	$93.90	5.563%	$99.1237	$99.12	$99.10	$99.10
Purchase #4	$94.32	13.497%	$107.0504	$107.05	$107.05	$107.10
Purchase #5	$111.27	6.848%	$118.8898	$118.89	$118.90	$118.90
Purchase #6	$31.86	13.236%	$36.077	$36.08	$36.10	$36.10
Purchase #7	$179.81	5.228%	$189.2105	$189.21	$189.20	$189.20
7 purchase totals =	$817.28		$892.3419	$892.34	$892.35	$892.40