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	$109.28	3.421%	$113.0185	$113.02	$113.00	$113.00
Purchase #2	$142.58	11.401%	$158.8355	$158.84	$158.85	$158.80
Purchase #3	$84.50	9.734%	$92.7252	$92.73	$92.75	$92.70
Purchase #4	$70.92	10.686%	$78.4985	$78.50	$78.50	$78.50
Purchase #5	$188.59	4.169%	$196.4523	$196.45	$196.45	$196.50
Purchase #6	$9.75	5.439%	$10.2803	$10.28	$10.30	$10.30
Purchase #7	$25.82	3.871%	$26.8195	$26.82	$26.80	$26.80
7 purchase totals =	$631.44		$676.6298	$676.64	$676.65	$676.60