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	$103.92	10.436%	$114.7651	$114.77	$114.75	$114.80
Purchase #2	$93.71	12.336%	$105.2701	$105.27	$105.25	$105.30
Purchase #3	$242.66	5.455%	$255.8971	$255.90	$255.90	$255.90
Purchase #4	$219.79	6.179%	$233.3708	$233.37	$233.35	$233.40
Purchase #5	$230.32	6.429%	$245.1273	$245.13	$245.15	$245.10
Purchase #6	$13.67	7.709%	$14.7238	$14.72	$14.70	$14.70
Purchase #7	$187.56	5.759%	$198.3616	$198.36	$198.35	$198.40
7 purchase totals =	$1,091.63		$1,167.5158	$1,167.52	$1,167.45	$1,167.60