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	$208.76	8.478%	$226.4587	$226.46	$226.45	$226.50
Purchase #2	$202.74	9.704%	$222.4139	$222.41	$222.40	$222.40
Purchase #3	$39.32	6.221%	$41.7661	$41.77	$41.75	$41.80
Purchase #4	$223.60	10.284%	$246.595	$246.60	$246.60	$246.60
Purchase #5	$215.56	3.184%	$222.4234	$222.42	$222.40	$222.40
Purchase #6	$40.56	9.246%	$44.3102	$44.31	$44.30	$44.30
Purchase #7	$132.43	7.230%	$142.0047	$142.00	$142.00	$142.00
7 purchase totals =	$1,062.97		$1,145.9720	$1,145.97	$1,145.90	$1,146.00