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	$134.29	8.643%	$145.8967	$145.90	$145.90	$145.90
Purchase #2	$202.65	5.807%	$214.4179	$214.42	$214.40	$214.40
Purchase #3	$69.25	4.235%	$72.1827	$72.18	$72.20	$72.20
Purchase #4	$138.29	7.700%	$148.9383	$148.94	$148.95	$148.90
Purchase #5	$122.42	13.400%	$138.8243	$138.82	$138.80	$138.80
Purchase #6	$66.82	7.868%	$72.0774	$72.08	$72.10	$72.10
Purchase #7	$184.54	13.765%	$209.9419	$209.94	$209.95	$209.90
7 purchase totals =	$918.26		$1,002.2792	$1,002.28	$1,002.30	$1,002.20