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	$218.88	10.539%	$241.9478	$241.95	$241.95	$241.90
Purchase #2	$212.85	10.315%	$234.8055	$234.81	$234.80	$234.80
Purchase #3	$81.30	12.854%	$91.7503	$91.75	$91.75	$91.80
Purchase #4	$31.78	8.795%	$34.5751	$34.58	$34.60	$34.60
Purchase #5	$75.25	4.553%	$78.6761	$78.68	$78.70	$78.70
Purchase #6	$86.46	3.809%	$89.7533	$89.75	$89.75	$89.80
Purchase #7	$13.30	4.659%	$13.9196	$13.92	$13.90	$13.90
7 purchase totals =	$719.82		$785.4277	$785.44	$785.45	$785.50