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	$33.50	12.546%	$37.7029	$37.70	$37.70	$37.70
Purchase #2	$72.38	7.798%	$78.0242	$78.02	$78.00	$78.00
Purchase #3	$168.97	4.387%	$176.3827	$176.38	$176.40	$176.40
Purchase #4	$18.68	4.566%	$19.5329	$19.53	$19.55	$19.50
Purchase #5	$143.96	8.145%	$155.6855	$155.69	$155.70	$155.70
Purchase #6	$6.34	8.765%	$6.8957	$6.90	$6.90	$6.90
Purchase #7	$146.94	3.508%	$152.0947	$152.09	$152.10	$152.10
7 purchase totals =	$590.77		$626.3186	$626.31	$626.35	$626.30