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	$90.37	5.296%	$95.156	$95.16	$95.15	$95.20
Purchase #2	$76.90	11.178%	$85.4959	$85.50	$85.50	$85.50
Purchase #3	$106.28	4.792%	$111.3729	$111.37	$111.35	$111.40
Purchase #4	$113.40	10.642%	$125.468	$125.47	$125.45	$125.50
Purchase #5	$108.63	10.503%	$120.0394	$120.04	$120.05	$120.00
Purchase #6	$230.74	6.333%	$245.3528	$245.35	$245.35	$245.40
Purchase #7	$237.94	7.582%	$255.9806	$255.98	$256.00	$256.00
7 purchase totals =	$964.26		$1,038.8656	$1,038.87	$1,038.85	$1,039.00