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	$128.51	3.366%	$132.8356	$132.84	$132.85	$132.80
Purchase #2	$13.82	12.170%	$15.5019	$15.50	$15.50	$15.50
Purchase #3	$136.35	4.660%	$142.7039	$142.70	$142.70	$142.70
Purchase #4	$131.82	8.246%	$142.6899	$142.69	$142.70	$142.70
Purchase #5	$133.34	9.791%	$146.3953	$146.40	$146.40	$146.40
Purchase #6	$98.75	10.520%	$109.1385	$109.14	$109.15	$109.10
Purchase #7	$196.67	6.755%	$209.9551	$209.96	$209.95	$210.00
7 purchase totals =	$839.26		$899.2202	$899.23	$899.25	$899.20