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	$154.94	13.331%	$175.5951	$175.60	$175.60	$175.60
Purchase #2	$94.39	3.712%	$97.8938	$97.89	$97.90	$97.90
Purchase #3	$71.90	9.715%	$78.8851	$78.89	$78.90	$78.90
Purchase #4	$28.39	13.153%	$32.1241	$32.12	$32.10	$32.10
Purchase #5	$35.56	11.290%	$39.5747	$39.57	$39.55	$39.60
Purchase #6	$47.34	4.176%	$49.3169	$49.32	$49.30	$49.30
Purchase #7	$39.27	13.579%	$44.6025	$44.60	$44.60	$44.60
7 purchase totals =	$471.79		$517.9922	$517.99	$517.95	$518.00