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	$111.72	5.383%	$117.7339	$117.73	$117.75	$117.70
Purchase #2	$17.97	13.388%	$20.3758	$20.38	$20.40	$20.40
Purchase #3	$189.83	3.746%	$196.941	$196.94	$196.95	$196.90
Purchase #4	$28.89	10.256%	$31.853	$31.85	$31.85	$31.90
Purchase #5	$85.87	7.684%	$92.4683	$92.47	$92.45	$92.50
Purchase #6	$6.64	9.236%	$7.2533	$7.25	$7.25	$7.30
Purchase #7	$36.89	3.589%	$38.214	$38.21	$38.20	$38.20
7 purchase totals =	$477.81		$504.8393	$504.83	$504.85	$504.90