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	$59.67	4.527%	$62.3713	$62.37	$62.35	$62.40
Purchase #2	$217.57	11.676%	$242.9735	$242.97	$242.95	$243.00
Purchase #3	$73.97	12.226%	$83.0136	$83.01	$83.00	$83.00
Purchase #4	$179.31	3.655%	$185.8638	$185.86	$185.85	$185.90
Purchase #5	$19.28	11.147%	$21.4291	$21.43	$21.45	$21.40
Purchase #6	$72.97	12.264%	$81.919	$81.92	$81.90	$81.90
Purchase #7	$133.87	12.808%	$151.0161	$151.02	$151.00	$151.00
7 purchase totals =	$756.64		$828.5864	$828.58	$828.50	$828.60