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	$168.85	11.722%	$188.6426	$188.64	$188.65	$188.60
Purchase #2	$45.86	6.399%	$48.7946	$48.79	$48.80	$48.80
Purchase #3	$103.52	8.778%	$112.607	$112.61	$112.60	$112.60
Purchase #4	$127.60	12.759%	$143.8805	$143.88	$143.90	$143.90
Purchase #5	$234.95	4.846%	$246.3357	$246.34	$246.35	$246.30
Purchase #6	$142.44	9.291%	$155.6741	$155.67	$155.65	$155.70
Purchase #7	$99.45	4.745%	$104.1689	$104.17	$104.15	$104.20
7 purchase totals =	$922.67		$1,000.1034	$1,000.10	$1,000.10	$1,000.10