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	$67.83	7.102%	$72.6473	$72.65	$72.65	$72.60
Purchase #2	$124.74	10.605%	$137.9687	$137.97	$137.95	$138.00
Purchase #3	$95.35	6.844%	$101.8758	$101.88	$101.90	$101.90
Purchase #4	$120.86	10.172%	$133.1539	$133.15	$133.15	$133.20
Purchase #5	$182.89	3.614%	$189.4996	$189.50	$189.50	$189.50
Purchase #6	$137.92	11.137%	$153.2802	$153.28	$153.30	$153.30
Purchase #7	$244.76	4.184%	$255.0008	$255.00	$255.00	$255.00
7 purchase totals =	$974.35		$1,043.4263	$1,043.43	$1,043.45	$1,043.50