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	$89.56	3.514%	$92.7071	$92.71	$92.70	$92.70
Purchase #2	$95.25	11.208%	$105.9256	$105.93	$105.95	$105.90
Purchase #3	$99.97	12.703%	$112.6692	$112.67	$112.65	$112.70
Purchase #4	$134.44	10.256%	$148.2282	$148.23	$148.25	$148.20
Purchase #5	$239.36	6.613%	$255.1889	$255.19	$255.20	$255.20
Purchase #6	$129.58	11.840%	$144.9223	$144.92	$144.90	$144.90
Purchase #7	$208.92	9.811%	$229.4171	$229.42	$229.40	$229.40
7 purchase totals =	$997.08		$1,089.0584	$1,089.07	$1,089.05	$1,089.00