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	$231.48	10.758%	$256.3826	$256.38	$256.40	$256.40
Purchase #2	$125.46	6.760%	$133.9411	$133.94	$133.95	$133.90
Purchase #3	$101.75	9.542%	$111.459	$111.46	$111.45	$111.50
Purchase #4	$178.73	9.863%	$196.3581	$196.36	$196.35	$196.40
Purchase #5	$55.67	9.314%	$60.8551	$60.86	$60.85	$60.90
Purchase #6	$60.62	7.694%	$65.2841	$65.28	$65.30	$65.30
Purchase #7	$33.96	13.637%	$38.5911	$38.59	$38.60	$38.60
7 purchase totals =	$787.67		$862.8711	$862.87	$862.90	$863.00