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	$55.38	6.536%	$58.9996	$59.00	$59.00	$59.00
Purchase #2	$102.96	7.826%	$111.0176	$111.02	$111.00	$111.00
Purchase #3	$95.27	8.651%	$103.5118	$103.51	$103.50	$103.50
Purchase #4	$243.84	12.815%	$275.0881	$275.09	$275.10	$275.10
Purchase #5	$249.35	10.689%	$276.003	$276.00	$276.00	$276.00
Purchase #6	$33.81	10.377%	$37.3185	$37.32	$37.30	$37.30
Purchase #7	$212.91	4.713%	$222.9444	$222.94	$222.95	$222.90
7 purchase totals =	$993.52		$1,084.8830	$1,084.88	$1,084.85	$1,084.80