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	$169.89	10.275%	$187.3462	$187.35	$187.35	$187.30
Purchase #2	$204.28	13.493%	$231.8435	$231.84	$231.85	$231.80
Purchase #3	$89.44	3.509%	$92.5784	$92.58	$92.60	$92.60
Purchase #4	$77.56	8.152%	$83.8827	$83.88	$83.90	$83.90
Purchase #5	$81.73	8.867%	$88.977	$88.98	$89.00	$89.00
Purchase #6	$228.51	9.726%	$250.7349	$250.73	$250.75	$250.70
Purchase #7	$30.63	4.598%	$32.0384	$32.04	$32.05	$32.00
7 purchase totals =	$882.04		$967.4011	$967.40	$967.50	$967.30