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	$224.37	7.472%	$241.1349	$241.13	$241.15	$241.10
Purchase #2	$236.39	9.533%	$258.9251	$258.93	$258.95	$258.90
Purchase #3	$249.30	12.650%	$280.8365	$280.84	$280.85	$280.80
Purchase #4	$49.54	4.303%	$51.6717	$51.67	$51.65	$51.70
Purchase #5	$85.46	5.391%	$90.0671	$90.07	$90.05	$90.10
Purchase #6	$62.59	4.107%	$65.1606	$65.16	$65.15	$65.20
Purchase #7	$141.57	8.572%	$153.7054	$153.71	$153.70	$153.70
7 purchase totals =	$1,049.22		$1,141.5013	$1,141.51	$1,141.50	$1,141.50