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	$25.52	5.389%	$26.8953	$26.90	$26.90	$26.90
Purchase #2	$112.32	4.149%	$116.9802	$116.98	$117.00	$117.00
Purchase #3	$170.50	11.607%	$190.2899	$190.29	$190.30	$190.30
Purchase #4	$43.89	12.700%	$49.464	$49.46	$49.45	$49.50
Purchase #5	$195.58	6.377%	$208.0521	$208.05	$208.05	$208.10
Purchase #6	$197.41	9.142%	$215.4572	$215.46	$215.45	$215.50
Purchase #7	$202.25	10.107%	$222.6914	$222.69	$222.70	$222.70
7 purchase totals =	$947.47		$1,029.8301	$1,029.83	$1,029.85	$1,030.00