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	$181.53	3.292%	$187.506	$187.51	$187.50	$187.50
Purchase #2	$215.69	3.356%	$222.9286	$222.93	$222.95	$222.90
Purchase #3	$52.57	5.564%	$55.495	$55.50	$55.50	$55.50
Purchase #4	$27.84	5.745%	$29.4394	$29.44	$29.45	$29.40
Purchase #5	$46.57	9.829%	$51.1474	$51.15	$51.15	$51.10
Purchase #6	$18.75	8.368%	$20.319	$20.32	$20.30	$20.30
Purchase #7	$173.61	12.197%	$194.7852	$194.79	$194.80	$194.80
7 purchase totals =	$716.56		$761.6206	$761.64	$761.65	$761.50