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	$105.98	8.591%	$115.0847	$115.08	$115.10	$115.10
Purchase #2	$37.59	3.384%	$38.862	$38.86	$38.85	$38.90
Purchase #3	$143.28	7.616%	$154.1922	$154.19	$154.20	$154.20
Purchase #4	$100.54	12.387%	$112.9939	$112.99	$113.00	$113.00
Purchase #5	$250.50	4.815%	$262.5616	$262.56	$262.55	$262.60
Purchase #6	$19.46	11.490%	$21.696	$21.70	$21.70	$21.70
Purchase #7	$54.25	10.394%	$59.8887	$59.89	$59.90	$59.90
7 purchase totals =	$711.60		$765.2791	$765.27	$765.30	$765.40