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	$183.32	10.668%	$202.8766	$202.88	$202.90	$202.90
Purchase #2	$140.66	3.451%	$145.5142	$145.51	$145.50	$145.50
Purchase #3	$44.29	10.652%	$49.0078	$49.01	$49.00	$49.00
Purchase #4	$161.97	3.333%	$167.3685	$167.37	$167.35	$167.40
Purchase #5	$239.53	6.835%	$255.9019	$255.90	$255.90	$255.90
Purchase #6	$127.62	13.250%	$144.5297	$144.53	$144.55	$144.50
Purchase #7	$93.52	13.180%	$105.8459	$105.85	$105.85	$105.80
7 purchase totals =	$990.91		$1,071.0446	$1,071.05	$1,071.05	$1,071.00