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	$142.67	6.671%	$152.1875	$152.19	$152.20	$152.20
Purchase #2	$41.61	4.571%	$43.512	$43.51	$43.50	$43.50
Purchase #3	$44.59	8.416%	$48.3427	$48.34	$48.35	$48.30
Purchase #4	$58.92	6.229%	$62.5901	$62.59	$62.60	$62.60
Purchase #5	$123.66	13.292%	$140.0969	$140.10	$140.10	$140.10
Purchase #6	$228.82	4.257%	$238.5609	$238.56	$238.55	$238.60
Purchase #7	$250.83	11.755%	$280.3151	$280.32	$280.30	$280.30
7 purchase totals =	$891.10		$965.6052	$965.61	$965.60	$965.60