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	$95.67	7.389%	$102.7391	$102.74	$102.75	$102.70
Purchase #2	$59.72	4.482%	$62.3967	$62.40	$62.40	$62.40
Purchase #3	$41.94	3.627%	$43.4612	$43.46	$43.45	$43.50
Purchase #4	$194.85	8.278%	$210.9797	$210.98	$211.00	$211.00
Purchase #5	$18.35	11.701%	$20.4971	$20.50	$20.50	$20.50
Purchase #6	$246.73	11.178%	$274.3095	$274.31	$274.30	$274.30
Purchase #7	$88.42	13.444%	$100.3072	$100.31	$100.30	$100.30
7 purchase totals =	$745.68		$814.6905	$814.70	$814.70	$814.70