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	$222.35	7.708%	$239.4887	$239.49	$239.50	$239.50
Purchase #2	$102.32	4.450%	$106.8732	$106.87	$106.85	$106.90
Purchase #3	$29.46	13.483%	$33.4321	$33.43	$33.45	$33.40
Purchase #4	$215.90	12.164%	$242.1621	$242.16	$242.15	$242.20
Purchase #5	$99.53	10.371%	$109.8523	$109.85	$109.85	$109.90
Purchase #6	$61.48	13.185%	$69.5861	$69.59	$69.60	$69.60
Purchase #7	$133.34	13.224%	$150.9729	$150.97	$150.95	$151.00
7 purchase totals =	$864.38		$952.3674	$952.36	$952.35	$952.50