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	$222.44	9.191%	$242.8845	$242.88	$242.90	$242.90
Purchase #2	$11.33	3.720%	$11.7515	$11.75	$11.75	$11.80
Purchase #3	$67.47	7.731%	$72.6861	$72.69	$72.70	$72.70
Purchase #4	$14.65	12.339%	$16.4577	$16.46	$16.45	$16.50
Purchase #5	$45.65	13.686%	$51.8977	$51.90	$51.90	$51.90
Purchase #6	$27.25	11.199%	$30.3017	$30.30	$30.30	$30.30
Purchase #7	$15.37	13.371%	$17.4251	$17.43	$17.45	$17.40
7 purchase totals =	$404.16		$443.4043	$443.41	$443.45	$443.50