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	$246.69	4.153%	$256.935	$256.94	$256.95	$256.90
Purchase #2	$20.69	9.841%	$22.7261	$22.73	$22.75	$22.70
Purchase #3	$150.93	6.816%	$161.2174	$161.22	$161.20	$161.20
Purchase #4	$197.43	5.187%	$207.6707	$207.67	$207.65	$207.70
Purchase #5	$209.55	11.347%	$233.3276	$233.33	$233.35	$233.30
Purchase #6	$72.70	12.866%	$82.0536	$82.05	$82.05	$82.10
Purchase #7	$47.40	10.853%	$52.5443	$52.54	$52.55	$52.50
7 purchase totals =	$945.39		$1,016.4747	$1,016.48	$1,016.50	$1,016.40