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	$47.65	13.339%	$54.006	$54.01	$54.00	$54.00
Purchase #2	$198.63	8.602%	$215.7162	$215.72	$215.70	$215.70
Purchase #3	$6.88	6.716%	$7.3421	$7.34	$7.35	$7.30
Purchase #4	$78.64	9.528%	$86.1328	$86.13	$86.15	$86.10
Purchase #5	$202.92	13.534%	$230.3832	$230.38	$230.40	$230.40
Purchase #6	$74.54	5.377%	$78.548	$78.55	$78.55	$78.50
Purchase #7	$64.64	7.575%	$69.5365	$69.54	$69.55	$69.50
7 purchase totals =	$673.90		$741.6648	$741.67	$741.70	$741.50