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	$199.73	12.142%	$223.9812	$223.98	$224.00	$224.00
Purchase #2	$200.68	9.127%	$218.9961	$219.00	$219.00	$219.00
Purchase #3	$179.66	9.143%	$196.0863	$196.09	$196.10	$196.10
Purchase #4	$40.86	3.837%	$42.4278	$42.43	$42.45	$42.40
Purchase #5	$205.86	12.342%	$231.2672	$231.27	$231.25	$231.30
Purchase #6	$194.50	11.723%	$217.3012	$217.30	$217.30	$217.30
Purchase #7	$90.64	10.371%	$100.0403	$100.04	$100.05	$100.00
7 purchase totals =	$1,111.93		$1,230.1001	$1,230.11	$1,230.15	$1,230.10