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	$199.71	11.421%	$222.5189	$222.52	$222.50	$222.50
Purchase #2	$127.64	11.607%	$142.4552	$142.46	$142.45	$142.50
Purchase #3	$229.49	11.528%	$255.9456	$255.95	$255.95	$255.90
Purchase #4	$6.43	4.391%	$6.7123	$6.71	$6.70	$6.70
Purchase #5	$206.38	9.844%	$226.696	$226.70	$226.70	$226.70
Purchase #6	$220.33	3.855%	$228.8237	$228.82	$228.80	$228.80
Purchase #7	$36.76	8.622%	$39.9294	$39.93	$39.95	$39.90
7 purchase totals =	$1,026.74		$1,123.0811	$1,123.09	$1,123.05	$1,123.00