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	$224.97	7.548%	$241.9507	$241.95	$241.95	$242.00
Purchase #2	$249.41	12.431%	$280.4142	$280.41	$280.40	$280.40
Purchase #3	$138.30	13.466%	$156.9235	$156.92	$156.90	$156.90
Purchase #4	$122.79	11.533%	$136.9514	$136.95	$136.95	$137.00
Purchase #5	$99.79	4.808%	$104.5879	$104.59	$104.60	$104.60
Purchase #6	$105.73	4.248%	$110.2214	$110.22	$110.20	$110.20
Purchase #7	$41.78	9.748%	$45.8527	$45.85	$45.85	$45.90
7 purchase totals =	$982.77		$1,076.9018	$1,076.89	$1,076.85	$1,077.00