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	$127.98	11.630%	$142.8641	$142.86	$142.85	$142.90
Purchase #2	$175.39	11.852%	$196.1772	$196.18	$196.20	$196.20
Purchase #3	$23.88	7.694%	$25.7173	$25.72	$25.70	$25.70
Purchase #4	$82.87	5.427%	$87.3674	$87.37	$87.35	$87.40
Purchase #5	$206.43	11.582%	$230.3387	$230.34	$230.35	$230.30
Purchase #6	$197.62	8.139%	$213.7043	$213.70	$213.70	$213.70
Purchase #7	$168.27	10.450%	$185.8542	$185.85	$185.85	$185.90
7 purchase totals =	$982.44		$1,082.0232	$1,082.02	$1,082.00	$1,082.10