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	$125.92	9.166%	$137.4618	$137.46	$137.45	$137.50
Purchase #2	$36.94	4.527%	$38.6123	$38.61	$38.60	$38.60
Purchase #3	$109.27	6.579%	$116.4589	$116.46	$116.45	$116.50
Purchase #4	$239.74	7.170%	$256.9294	$256.93	$256.95	$256.90
Purchase #5	$116.33	9.159%	$126.9847	$126.98	$127.00	$127.00
Purchase #6	$134.55	9.201%	$146.9299	$146.93	$146.95	$146.90
Purchase #7	$85.87	10.801%	$95.1448	$95.14	$95.15	$95.10
7 purchase totals =	$848.62		$918.5218	$918.51	$918.55	$918.50