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	$120.66	5.602%	$127.4194	$127.42	$127.40	$127.40
Purchase #2	$228.75	11.545%	$255.1592	$255.16	$255.15	$255.20
Purchase #3	$113.33	12.558%	$127.562	$127.56	$127.55	$127.60
Purchase #4	$247.94	3.705%	$257.1262	$257.13	$257.15	$257.10
Purchase #5	$72.26	6.709%	$77.1079	$77.11	$77.10	$77.10
Purchase #6	$169.47	4.570%	$177.2148	$177.21	$177.20	$177.20
Purchase #7	$35.51	7.315%	$38.1076	$38.11	$38.10	$38.10
7 purchase totals =	$987.92		$1,059.6971	$1,059.70	$1,059.65	$1,059.70