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	$67.72	7.587%	$72.8579	$72.86	$72.85	$72.90
Purchase #2	$42.40	8.344%	$45.9379	$45.94	$45.95	$45.90
Purchase #3	$117.30	5.334%	$123.5568	$123.56	$123.55	$123.60
Purchase #4	$155.67	9.254%	$170.0757	$170.08	$170.10	$170.10
Purchase #5	$126.65	5.794%	$133.9881	$133.99	$134.00	$134.00
Purchase #6	$164.83	4.512%	$172.2671	$172.27	$172.25	$172.30
Purchase #7	$246.90	3.562%	$255.6946	$255.69	$255.70	$255.70
7 purchase totals =	$921.47		$974.3781	$974.39	$974.40	$974.50