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	$127.27	12.694%	$143.4257	$143.43	$143.45	$143.40
Purchase #2	$148.82	9.620%	$163.1365	$163.14	$163.15	$163.10
Purchase #3	$65.61	11.152%	$72.9268	$72.93	$72.95	$72.90
Purchase #4	$221.79	7.379%	$238.1559	$238.16	$238.15	$238.20
Purchase #5	$229.27	12.761%	$258.5271	$258.53	$258.55	$258.50
Purchase #6	$118.68	7.642%	$127.7495	$127.75	$127.75	$127.70
Purchase #7	$193.90	5.802%	$205.1501	$205.15	$205.15	$205.20
7 purchase totals =	$1,105.34		$1,209.0716	$1,209.09	$1,209.15	$1,209.00