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	$45.45	13.762%	$51.7048	$51.70	$51.70	$51.70
Purchase #2	$89.87	10.153%	$98.9945	$98.99	$99.00	$99.00
Purchase #3	$219.83	6.613%	$234.3674	$234.37	$234.35	$234.40
Purchase #4	$171.62	5.523%	$181.0986	$181.10	$181.10	$181.10
Purchase #5	$81.32	5.131%	$85.4925	$85.49	$85.50	$85.50
Purchase #6	$111.29	11.252%	$123.8124	$123.81	$123.80	$123.80
Purchase #7	$240.73	6.229%	$255.7251	$255.73	$255.75	$255.70
7 purchase totals =	$960.11		$1,031.1953	$1,031.19	$1,031.20	$1,031.20