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	$238.95	3.715%	$247.827	$247.83	$247.85	$247.80
Purchase #2	$80.81	6.858%	$86.3519	$86.35	$86.35	$86.40
Purchase #3	$103.85	5.742%	$109.8131	$109.81	$109.80	$109.80
Purchase #4	$51.51	7.844%	$55.5504	$55.55	$55.55	$55.60
Purchase #5	$111.33	4.824%	$116.7006	$116.70	$116.70	$116.70
Purchase #6	$87.49	3.233%	$90.3186	$90.32	$90.30	$90.30
Purchase #7	$239.72	10.247%	$264.2841	$264.28	$264.30	$264.30
7 purchase totals =	$913.66		$970.8457	$970.84	$970.85	$970.90